Next Man Up: Which NFL Players Are Turning Heads With Replacement Play?

The new year often signals change. The NFL doesn't operate on a normal calendar, though. 

Teams shift every week due to injuries, performance or matchups. Hence, numerous individuals already staked their claims to expanded roles in 2018 after entering the season free of expectations. 

Some replacements create a bigger impact than others, however. 

Ten individuals deserve recognition after not being Week 1 starters nor first- or second-round draft picks expected to take over a starting role. 

Their teams couldn't have foreseen this level of success, but each of the squads is benefiting from these burgeoning stars.

Just call Minnesota Vikings quarterback Case Keenum the new Million Dollar Man, because everyone has a price, and some team will pay for his services. 

Sam Bradford entered the season as the Vikings' starting quarterback only to be plagued by a lingering knee issue that put him on injured reserve. At the time, Teddy Bridgewater hadn't been medically cleared from his 2016 knee injury. 

Keenum became the starter in Week 2 and held the position even with Bridgewater's return. The undrafted free agent ranks fourth overall in completion percentage (67.3 percent), seventh in quarterback rating (98.1) and 12th in passing yards (3,358), touchdowns (21) and yards per attempt (7.43). 

More importantly, the Vikings offense evolved with Keenum behind center. His mobility allowed offensive coordinator Pat Shurmur to open up the playbook. 

"It's a lot better than it was, and I think we still have some room to grow," Keenum said, per ESPN.com's Courtney Cronin. "The more time we spend in meeting rooms watching film, talking through defenses. We're getting more and more on the same page and seeing things through the same set of eyes. I think that's important for a coordinator and a quarterback."

Keenum is set to enter free agency after this season, and he should have many suitors. Right now, he's the straw that stirs the Vikings' drink. Mead, I believe. Skol.

Life is good for the San Francisco 49ers and quarterback Jimmy Garoppolo. The organization found its franchise quarterback, and Garoppolo is about to get paid.

"Max the man out," fullback Kyle Juszczyk said, per ESPN.com's Nick Wagoner. "He deserves it. I think he's everything that we've been looking for."

The quarterback's limited sample size in New England skewed his market, and the Patriots moved him before the Oct. 31 trade deadline for a 2018 second-round pick. What a bargain for the 49ers. 

Head coach Kyle Shanahan and his staff were patient with Garoppolo. The organization allowed the 26-year-old signal-caller to get comfortable and learn the playbook before placing him in the starting lineup.

Shanahan removed rookie C.J. Beathard from the lineup Dec. 3. The 49ers are 4-0 since Garoppolo became the starter, and he's thrown for more yards (1,250) in his first four starts with a new team than any other quarterback in NFL history, per NBC Sports Bay Area's Matt Maiocco. 

The production is nice. However, Garoppolo's impeccable mechanics, calm demeanor and attitude around teammates make everyone in the organization feel better about the future. 

"Football's fun again," 11th-year left tackle Joe Staley exclaimed after Sunday's 44-33 victory over the Jacksonville Jaguars, per NFL Media's Michael Silver. 

The Baltimore Ravens acquired running back Alex Collins after the Seattle Seahawks released him during the final roster cutdown prior to the start of the regular season.

Collins wasn't even added to the active roster. He signed a practice squad agreement before getting a chance to contribute in Week 2. He officially became the starter four weeks later with a 74-yard effort against the Chicago Bears and hasn't come out of the lineup since. 

Despite the Ravens' offensive limitations, Collins ranks 10th overall with 895 rushing yards and 4.7 yards per carry. He produced while playing behind a revamped offensive front that features three new starters. 

"He's a great player," center Ryan Jensen said, per ESPN.com's Jamison Hensley. "He's really hot. He's making a lot of good plays for us."

Baltimore owns the league's 26th-ranked passing offense. Joe Flacco's wide receivers are limited, and Collins will be a big part of the team's playoff push. The 9-6 Ravens own the AFC's fifth seed, and their second-year runner will be the focal point of their approach against more well-rounded postseason opponents. 

Collins provided an identity when Flacco and Co. failed to establish an early-season rhythm. He'll continue to be the tone-setter in the coming weeks and possibly into next season. Not bad for a back who couldn't crack the Seahawks rotation. 

Meet this year's likely NFL Offensive Rookie of the Year. New Orleans Saints running back Alvin Kamara is well on his way to earning the honor because he's nearly impossible to defend. 

According to Pro Football Focus, Kamara owns the NFL's highest elusive rating, which entails how successful a runner is past his blockers.

"It does [slow down]," Kamara said about the game, per ESPN.com's Mike Triplett. "I was thinking about it the other day, like I kind of go into Matrix mode, and I’m just like, 'OK, him, him, him—I got these three guys.' It's not a full-speed full head of steam all the time. It's calculated, like, 'All right, well, I'm gonna slow down a little bit, make him think I'm cutting back, and then speed up.' It's a lot of downshifting, upshifting."

He's also the first rookie in 52 years with five rushing and receiving touchdowns, per NFL senior director of football communications Randall Liu. Kamara and Mark Ingram are the first teammates in NFL history to each manage 1,300 scrimmage yards and 10 total touchdowns. The first-year runner's 6.2 yards per carry leads the league, too. 

Of course, an argument could and should be made for fellow third-round pick Kareem Hunt. After all, Hunt ranks second overall with 1,292 rushing yards. The Kansas City Chiefs back also has 455 receiving yards and 10 total touchdowns. 

But Kamara changed the complexion of the Saints offense, even though he's still not considered a starter.  

New Orleans came into this season expecting Ingram and future Hall of Fame back Adrian Peterson to carry the load. Peterson never fit Sean Payton's offense, though. Instead, Kamara became a bigger part of the scheme with each passing week. Now, the entire system is built around the rookie's ability to exploit mismatches in and out of the backfield. 

The Miami Dolphins' 2017 campaign hasn't gone according to plan. 

Last year's playoff squad featured the NFL's ninth-ranked rushing attack, with Jay Ajayi leading the way. Ajayi is no longer a part of the team, as the Dolphins traded him to the Philadelphia Eagles in late October. Miami isn't in the playoff mix, either. The running game, meanwhile, ranks 28th overall. 

However, the coaching staff appears to have found a new feature back in Kenyan Drake. Since he took over as the starter in Week 12 against the New England Patriots, the 2016 third-round pick carried the ball 86 times for 389 yards, including a pair of 100-yard outings.  

"It's progress. He just continues to grow," Dolphins offensive coordinator Clyde Christensen said last week, per the Sun Sentinel's Omar Kelly. "I was kind of teasing him, it's not that painful to kind of be mature, and he said, 'No, it really isn't.' But he hasn't quite arrived yet." 

Drake's 569 rushing yards are 104 more than Ajayi had before he was traded, and they've come on 19 fewer carries.

The team moved its previous starter in part due to a poor attitude, according to Kelly. The decision wasn't part of a grand plan to work Drake into a lead role. The organization thought it found value for a back it no longer wanted. 

Even so, the second-year runner developed into a pleasant surprise. Now, the Dolphins' 2018 plans will include Drake in the backfield alongside returning quarterback Ryan Tannehill.

The rash of injuries the Jacksonville Jaguars suffered at wide receiver could be deemed an epidemic. It's a good thing the organization had the foresight to sign undrafted wide receiver Keelan Cole out of Kentucky Wesleyan College, a Division II program. 

Allen Robinson, Rashad Greene, Arrelious Benn and Jaelen Strong all have been placed on injured reserve. Dede Westbrook, Allen Hurns and Marqise Lee have already missed a combined 16 games due to injuries, and the number will likely grow in Week 17 since Lee and Hurns continue to deal with ankle issues. 

Cole had to play because the Jaguars had no other options, and he responded well. 

"I think maybe in the [Week 7] Indianapolis game it was kind of, 'Let's figure out if Keelan can play," quarterback Blake Bortles said, per the Florida Times-Union's Phillip Heilman. "Let's give him some opportunities to make some plays.’ And ever since then, he’s kind of been on a tear."

The rookie didn't immediately produce, but he developed into the team's top target in short order. Cole caught 19 passes for 442 yards and three touchdowns during the past four contests, and he now leads the team with 715 receiving yards. 

The 24-year-old receiver provides the Jaguars with long-term security, too. Both Robinson and Lee are free agents after the season, and Cole's presence alongside Hurns, Westbrook and Jaydon Mickens might sway the organization from offering them large contracts.  

The value of a good offensive lineman, particularly a promising young blocker, is at an all-time high.

The league is trending toward massive free-agent paydays for veterans, because incoming talent has struggled. The proliferation of college spread offenses requires less nuanced line play. There's far less of an emphasis placed on technique, which is forsaken in favor of speed and athleticism. 

Thus, NFL organizations look toward programs that run pro-style blocking concepts in an attempt to have more prepared linemen at a younger age. 

Chase Roullier played guard and center for head coach Craig Bohl at Wyoming. Bohl started the North Dakota State dynasty that featured breakout NFL star quarterback Carson Wentz. He brought the same system to the Laramie, and the experience allowed Washington's sixth-round pick to develop into a rookie starter. 

"He's going to be a very good center for a long time here," head coach Jay Gruden said in mid-December, per ESPN.com's John Keim. "I love his demeanor. He's got great strength, great lower body strength, and he gets off the ball."

Roullier officially took over for Spencer Long in Week 15 once the organization placed the veteran on injured reserve due to knee tendinitis. The first-year blocker started four games earlier in the season, too.

With Long and left guard Shawn Lauvao about to become free agents, Roullier should remain a starter in Washington beyond the 2017 campaign. 

Robert Nkemdiche was supposed to bring balance to the Arizona Cardinals defensive front. The standout talent hasn't lived up to expectations, though. 

Instead, Olsen Pierre moved into the starting lineup on Nov. 9, and he's been far more effective. The 2015 undrafted free agent spent all of last year on the Cardinals' practice squad before eliciting the coaching staff's attention during the summer. 

"He's a hell of a pass-rusher," head coach Bruce Arians said in June, per Kyle Odegard of the Cardinals' official site. "He's up to 298 (pounds). He's got length. He might be our best inside pass-rusher right now."

Arians comments proved to be prophetic, as Pierre is second on the team with 4.5 sacks.

An interior pass-rusher is worth his weight in gold since the ability to collapse a pocket makes a team's edge-rushers even better. The Cardinals happen to feature the NFL's current sack leader in Chandler Jones. 

In the third-year defensive lineman's six starts, he has three sacks and five quarterback hits. He's quick off the snap with long arms and improved strength, which makes him a handful for most interior blockers.  

Pierre further proves a player doesn't need to be the No. 1 overall high school recruit or a first-round pick to become a productive professional.

Not enough is being made of the New Orleans Saints' defensive turnaround. After years of futility, the Saints rank 15th overall in total defense. 

Their revamped secondary is the driving force behind their recent success. Rookie cornerback Marshon Lattimore receives most of the attention since he's a Defensive Rookie of the Year candidate, but second-year undrafted free agent Ken Crawley has also developed into an impressive bookend. 

With Delvin Breaux dealing with a fractured fibula, the Saints needed another starting cornerback. P.J. Williams opened the regular season as a starter, but he eventually gave way to Crawley, who has started 12 contests. 

Crawley played extensively last season, but he never appeared comfortable. His role expanded this year because of Lattimore being injured earlier in the year and Williams being benched for disciplinary reasons. The long and lean defensive back made the most of the opportunity by showing improved instincts. He's second on the team with 14 deflected passes. 

"I'm getting smarter as the season is going, watching more tape and just trusting it," Crawley said in early October, per the Times-Picayune's Josh Katzenstein. "I just say I've been trusting what I'm seeing out there."

Alongside safeties Vonn Bell and Marcus Williams, Crawley and Lattimore should form a young and exciting secondary for years to come.

Los Angeles Rams rookie safety John Johnson III made a strong first impression in his first career start against the Seattle Seahawks in Week 5. He deflected two passes and snagged his first career interception, which he returned for 69 yards. 

"He made a couple splash plays," head coach Sean McVay said after the game, per the Los Angeles Times' Lindsey Thiry and Gary Klein. "John's a player that since he's got here, he's continued to grow. He's a player that we have a lot of confidence in and expecting him to continue to improve."

His play prompted the Rams front office to release former starter Maurice Alexander. This year's third-round pick has started nine more games since his standout initial performance, and he ranks third on the team with 71 total tackles. He is also second on the Rams with 11 deflected passes. 

Johnson became entrenched as a starter in a secondary that ranks sixth overall in pass defense. The rookie's range allows him to be an interchangeable piece. The Boston College product is technically a strong safety, but he can easily drop into the deep third and provide sideline-to-sideline coverage. 

Lamarcus Joyner is one of the league's most versatile defenders, as he defends the slot, plays in the box and drops into deep coverage. The 6'0", 204-pound Johnson is the perfect complement to Joyner's skill set. 

All stats via Pro Football Reference or NFL.com unless otherwise noted. Contract numbers courtesy of Spotrac.