It takes 53 men to make up an NFL roster, but some players go beyond the role of roster-filler and become unmatched assets for their teams as they try to win games.
These specific players are, in a sense, irreplaceable, either for what they bring to the game on their own or the likely devastating results of using the next player down on the depth charts.
Here are the most irreplaceable players on every NFL roster.
While much of the offense for the Arizona Cardinals has been a major question mark, one major piece of stability has been wide receiver Larry Fitzgerald.
One of the most athletically and mentally gifted players in the league, Fitzgerald has a knack for making even the least-encouraging quarterback prospect look like a legitimate starter.
Tough (if not impossible) to replace: Patrick Peterson
It's tough not to give a lot of credit for the success of the Atlanta Falcons to their quarterback Matt Ryan. While 2011 may not have been the best statistical year in the league, it shows the team had a lot of hopes for its future and the progress made by its man under center.
Already, Ryan has piled up the yardage and touchdowns and is slowly moving his way up the team's record books.
His challenge in 2012: Track down his first playoff win.
Tough (if not impossible) to replace: Michael Turner
The Baltimore Ravens are more than just a defensive powerhouse, and a lot of that change in perception comes with the large jump in their offense through players like running back Ray Rice. Just a few years into the pro game, Rice has already won over the toughest fans with his slashing running style and ridiculous production. His 1364 rushing yards in 2011 were good enough for second best in the league.
If the Ravens want to go from division challenger to Super Bowl contender, they'll need stellar performances from players like Rice to make it happen.
Tough (if not impossible) to replace: Terrell Suggs
His team's biggest weapon prior to his loss for the tail end of last season, Buffalo Bills running back Fred Jackson's 2012 return should be very exciting
One of the breakout stars of 2011, Jackson used his immense speed and vision to find holes in the defense and build up speed to get away. Even more impressive for Jackson was that his skills were more than enough to hold off more recognizable names from the top job, including C.J. Spiller.
I also have a sneaking suspicion that he'll go higher in fantasy football drafts in 2012 than last year, where his wife was hesitant to use a late-round pick to grab her husband.
Tough (if not impossible) to replace: Stevie Johnson
He may only be in his second year, but Carolina Panthers quarterback Cam Newton has played a huge role in his team's success, and will continue to do so.
Newton's rookie season was nothing short of spectacular, as the young passer shattered several rookie and general records with both his ability to pass and to run. One writer stated Newton's rookie campaign was the best season for a rookie in league history.
Even more encouraging, Newton has appeared to gone right back to work to get his game moving in the right direction. Asked about his progress so far this offseason, he promised his own game had improved "through the roof."
Look for the team's win total to rise if the Panthers see even the most incremental improvement in their defensive production.
Tough (if not impossible) to replace: Steve Smith
While Chicago Bears quarterback Jay Cutler may not be the most popular figure in town, his value was magnified this past season as the team was led by the shockingly-bad Caleb Hanie, who parlayed a stellar playoff appearance into multiple starts.
Hanie's completion percentage of 50 percent may be reasonable, but his nearly 9 percent interception rate was measured late last season as one of the worst ever.
In other words, long live Jay Cutler.
Tough (if not impossible) to replace: Matt Forte
The Cincinnati Bengals were one of the major surprise stories of 2011, and a lot of that had to do with the excellent pairing of quarterback Andy Dalton and wide receiver A.J. Green. The two rookies quickly became one of the more exciting passing duos in the league.
So why does Dalton get the nod for this list? His slightly-better longevity. While Green was limited by some injuries late in the regular season, Dalton managed to make it through the entire season without missing any time.
However, the difference between the two is so minimal that it could be said both of them cannot be meaningfully replaced in any possible way.
Tough (if not impossible) to replace: A.J. Green
The Cleveland Browns may not have the sexiest offense or most effective defense, but they do have one of the league's best protectors in left tackle Joe Thomas.
Among his numerous accolades, Thomas has been named to the past three All-Pro teams and made the past five Pro Bowl rosters.
Signed to a whopping seven-year contract extension, Thomas is the strength of the team's line today and will continue to fulfill that role into the foreseeable future.
Tough (if not impossible) to replace: D'Qwell Jackson
The Dallas Cowboys have to feel confident with quarterback Tony Romo, who enters into 2012 on a real high note.
In addition to throwing the second-most yards and touchdowns in a season of his career, he did so while making significant drops to the number of interceptions and turnovers he committed.
With the team taking dramatic steps to shore up its defense, look for the Cowboys to maybe add some more wins to their record if Romo can keep up the good work.
Tough (if not impossible) to replace: DeMarcus Ware
It's tough to put Denver Broncos quarterback Peyton Manning in this spot before he's even played a snap with his new team, but he is truly irreplaceable in the classic sense of the word: The team doesn't have anybody ready to lead behind him.
Rookie Brock Osweiler may be an interesting project for a few years down the road, but his lack of accuracy only spells out problems for the team if it were to throw him into action.
The quality of the team's third passer, Caleb Hanie, should only inspire more worries on the team's state should Manning miss time this coming year.
In other words, Manning cannot not get hurt if the Broncos want to win big this year.
Tough (if not impossible) to replace: Von Miller
There's not much that can be added to the mass amounts of praise showered on Detroit Lions wide receiver Calvin Johnson, whose athleticism and hard work have propelled him to megastar status in the league and with its fans.
Finally pairing with a healthy Matthew Stafford, Johnson set career marks in both receiving yards and touchdowns as the Lions made the playoffs for the first time in over a decade.
Johnson's effort was rewarded with a gigantic contract extension worth up to $132 million, said to be the largest for a non-quarterback in league history.
Tough (if not impossible) to replace: Ndamukong Suh
Quarterback Aaron Rodgers is by far the best player on the talented Green Bay Packers roster. The league's MVP in 2012, Rodgers has been the main face of the team's return to prominence, confounding opposing defenses with his precision passing and smart decision making.
More important in my mind, Rodgers effectively took over the mantle as starting quarterback from a player many faithful Packers fans would have otherwise considered irreplaceable: Brett Favre.
Tough (if not impossible) to replace: Clay Matthews
While injuries hobbled Houston Texans wide receiver Andre Johnson for much of 2011, his production could not be replaced by other players on the roster.
While other positions, like quarterback and running back, saw talent stepping up as far as three players down the depth chart, Johnson's pass catching and ability to break from opposing defenders was something that could not be performed by a backup. Much of the team's passing success was filtered to its running backs.
Texans fans can only hope Johnson can make a return to 100 percent, as the Texans look to build on their first playoff appearance in franchise history in 2011.
Tough (if not impossible) to replace: Arian Foster
It's only fitting that in an offseason of contract purging and rebuilding, wide receiver Reggie Wayne was welcomed back with a new deal this offseason.
Pairing with Peyton Manning, Wayne proved himself as one of the league's most dynamic receivers and consistent contributors.
As his reward for his loyalty to the team, Wayne will get a spot on the ground floor of the Colts' rebuilding effort and a chance to serve as a major weapon for incoming rookie quarterback Andrew Luck.
Tough (if not impossible) to replace: Dwight Freeney
There isn't enough that can be said for the effort of running back Maurice Jones-Drew, the league's rushing leader in 2011.
Playing against defenses that stacked the box against him, Jones-Drew was still able to succeed and put up several hundred more yards than his nearest challenger, Baltimore Ravens running back Ray Rice.
With more uncertainty looming for the Jaguars offense in 2012 based on the development of quarterback Blaine Gabbert, there's no doubt Jones-Drew's contributions will be needed more than ever.
Tough (if not impossible) to replace: Paul Posluszny
The impact of the loss of running back Jamaal Charles cannot be understated for the Kansas City Chiefs in 2011, as the team dropped from the best team rushing attack the previous year to the middle of the pack.
Charles, who has been one of the league's biggest contributors in the past few seasons, has been effective in both the passing and rushing games. In losing him, the Chiefs was forced to adjust to a committee of backs that could not collectively match what Charles could do.
Look for the Chiefs to excel should Charles return to anywhere close to his 2010 peak.
Tough (if not impossible) to replace: Tamba Hali
One of the Miami Dolphins' defensive leaders, defensive tackle Paul Soliai was critical in the team's rushing defense, which ranked third in the league in 2011.
Soliai surprised many by returning to the team with a new deal in March. His return should be a big boost as the team makes adjustments to its formations for 2012.
Soliai's greatest skill may be his versatility, as he has the ability to play both in the interior or the exterior of the defensive line, boosting his already-high value to the defensive unit.
Tough (if not impossible) to replace: Cameron Wake
If the Minnesota Vikings didn't know the value of running back Adrian Peterson, they will soon get a sharp reminder, as he is still recovering from a knee injury late last season. His return date has not been set yet.
Peterson has been one of the league's best runners, leading the league in yardage and touchdowns for the five-season period since his rookie year of 2007. An ESPN analysis (included in the above link) showed that Peterson had produced the fifth-most touchdowns of any player in his first five years in the league, trailing greats including Jerry Rice, Emmitt Smith and LaDainian Tomlinson.
Should Peterson's return date get pushed back in a major way, look for the Vikings' hopes for the season to crash down harder than the roof of the Metrodome.
Tough (if not impossible) to replace: Jared Allen
While the cop-out answer would to be that no one irreplaceable with the New England Patriots under Bill Belichick, I'd like to take this in a different direction.
Instead of the safe choice with quarterback and team MVP Tom Brady, I'd say tight end Rob Gronkowski may be a tougher player to replace.
Time travel with me back to 2008, when Brady was injured in the first game of the season. The Patriots, turning to then-backup Matt Cassell, were able to navigate through the season pretty effectively, just falling short of the playoffs despite a record well over .500.
However, the injury to Gronkowski during the 2011 playoffs was insurmountable. Gronkowski, a vital player in the team's red-zone schemes, injured his ankle during the AFC Championship Game, limiting his effectiveness during the Super Bowl. While he still managed to hit the field, the tight end was used as little more than a distraction, with the one big pass heading his way leading to an interception.
With nobody fully able to replicate that kind of production, the injury to Gronkowski could have been the difference as the Patriots would fall in a close game to the New York Giants.
Tough (if not impossible) to replace: Tom Brady, especially with the question marks about the team's current backups.
The New Orleans Saints may not realize how lucky they have it in employing Drew Brees, one of the league's most exemplary players and overall role models. Fans may think they see one of the league's most irreplaceable stars, but it seems that Saints management looks at it differently.
The team appears to be short changing their star just as he comes off his best season as a pro, a year where he shattered nearly every single-season record imaginable for NFL quarterbacks.
For a franchise that could use a positive story, the re-signing of Brees would be something that would be nice to see.
Also tough to replace: Darren Sproles
One of the league's most clutch players, quarterback Eli Manning has been the difference in both of his team's Super Bowl wins.
In both instances, Manning has led his team on a game-winning drive late in the game, when the defenses of the New England Patriots were keying in to make a critical stop.
Despite the pressure, Manning finished the job, securing the wins in the most unlikely of fashions.
I'm not sure there are too many quarterbacks, or players overall in the league, who could excel in those tense situations like Manning could.
Also tough to replace: Jason Pierre-Paul
New York Jets cornerback Darrelle Revis has made it simple for opposing quarterbacks, challenging them at every turn, as if to say, "Throw at me at your own peril."
Most quarterbacks heed that advice, and as a result it seems the Jets have one less marquee receiver to worry about in their defensive game plan every week.
Tough (if not impossible) to replace: David Harris
How many players can guarantee field position quite like Oakland Raiders punter Shane Lechler? Not many.
Every week, the punter seems to prove his value to the team, hitting punts like this 80-yard smash early in the 2011 season (which really was more like a 90-yard punt given his position on the field).
Even more encouraging is that Lechler's success has no end in sight. For a team that seems in disarray at the moment with a new coaching regime and roster changes across the board, even the smallest certainties are a very good thing to see.
Tough (if not impossible) to replace: Darren McFadden
The Philadelphia Eagles were able to account for injuries at the quarterback position in 2011, but the team had few options were running back LeSean McCoy to go out of the picture.
McCoy has proven himself as one of the league's most effective backs, finishing in fifth for rushing yards and first in touchdowns scored.
Also, would you trust your offense to this kind of backup play?
Tough (if not impossible) to replace: Jason Babin
The unquestioned emotional leader of the Steelers' defense, Polamalu has a unique ability to fly across the field, showing an unmatchable range in pursuing tackles and sniffing out big plays.
Look for Polamalu to continue to serve as a face of a very intimidating Steelers' defensive unit as it looks to make up for an embarrassing playoff exit last season.
Tough (if not impossible) to replace: Ben Roethlisberger
While many of the team's offensive parts have parted ways in the past few years, including Darren Sproles and more recently Vincent Jackson, Rivers has found and should continue to find ways to succeed.
Look for him to pair up nicely with new targets Robert Meachem and Eddie Royal as the Chargers look to challenge for an AFC West title and their first playoff bid since 2009.
Tough (if not impossible) to replace: Antonio Gates
The San Francisco 49ers have one of the best defenses in the game (especially against the rush), and that success is in large part due to its anchor, linebacker Patrick Willis.
A mix of intelligence, athletic ability and intuition, Willis is slowly creeping into the conversation about great linebackers with players like Ray Lewis.
With all of their defensive starters back in 2012, look for the Niners to continue their stingy ways with opposing offenses.
Tough (if not impossible) to replace: Vernon Davis
Seattle Seahawks running back Marshawn Lynch has proven to be one of the league's most fierce backs, rising to become one of the league's better-known names following this run in the 2010 playoffs.
Since that time, Lynch has been one of the key contributors to an offense that for large portions of the year failed to get it done through the 2011 season. Though those struggles meant several opponents stacked the box against him, Lynch was still able to pull in some pretty respectable rushing stats for the year.
With some more stability in the picture for the team's quarterback situation following the signing of Matt Flynn, look for Lynch, better known as Beast Mode, to charge back into the top of the league's leaderboard for rushing yards.
Tough (if not impossible) to replace: Red Bryant
It's a real shame the St. Louis Rams have not been winning more, because as a result many people are missing out on how special of a talent running back Steven Jackson has been and still can be.
Jackson, who has seen his fair share of injuries during the course of his career, finished off his seventh 1,000-yard rushing season in a row in 2011.
For a team that has struggled in the passing game with injuries at the quarterback position, Jackson's contributions have been by all accounts irreplaceable.
Tough (if not impossible) to replace: Chris Long
The Tampa Bay Buccaneers may have one of the youngest rosters in the league, but they also get a huge boost from one of their more experienced members of the defense, cornerback Ronde Barber.
Barber still finds himself as one of the more consistent defenders in the league, despite hitting the age of 37.
Bucs management have already tabbed a move to safety for Barber, citing his skills and the team's need with the looming loss of Aqib Talib.
Tough (if not impossible) to replace: Vincent Jackson
With limited help in the receiving corps, especially after the loss of wide receiver Kenny Britt, Tennessee Titans wide receiver Nate Washington has made himself almost indispensable.
In a pretty conservative Titans passing attack, he came away with 74 receptions and 1,023 receiving yards last season, the first time a receiver on the team had passed that yardage mark since 2004.
Look for Washington to play a big role in 2012, even with Britt returning to the roster.
Tough (if not impossible) to replace: Rob Bironas
The Washington Redskins defense was a very pleasant surprise in 2011, and from that unit, linebacker London Fletcher has proven himself to be irreplaceable.
He has done so despite just turning 36, long past the time many players hang it up for good. Despite his age, Fletcher proved his mettle, leading the league in tackles for the year.
As the focus for the team moves to its offense and new quarterback Robert Griffin III, contributions from talented veterans like Fletcher will become all the more necessary for the team's success.
Tough (if not impossible) to replace: Brian Orakpo