No player is irreplaceable. You can't afford to consider any individual player irreplaceable because no one is immune to injury (first-round picks Jacoby Ellsbury and Matt Kemp) or extended slumps (Tim Lincecum and Justin Upton).
However, these 10 players are either great in so many different areas that they might carry your team, or they are elite in a few areas to the point that they can almost win you a category by themselves. Losing these players is not a death sentence to the team (like losing an elite QB or RB can be in fantasy football), but will significantly hamper your title hopes.
Note: Don't look for closers here. There will always be more closers available.
At the break, Ryan Braun sits at .306 with 24 HR, 15 SB, 61 RBI and 56 runs scored. Braun is equally valuable in head to head leagues as well as roto formats because he does the same stuff day-in-day-out the entire season.
Braun is batting .293 with a 1.065 OPS against left-handed pitchers. He is batting .310 with a .966 OPS against right-handers. He has 13 HR and six steals at home with 11 HR and nine steals on the road. He batted .294 in April, .323 in May, and .319 in June.
Braun is as safe as they come. The offseason controversy has not slowed him. Losing Prince Fielder has not slowed him. Rickie Weeks falling off the table has not slowed him. If you own Braun, congratulations. If you want him, prepare to pony up.
Justin Verlander is averaging 7.4 innings per start with five complete games in 18 starts. Therein lies his value... you know, after the 2.58 ERA, 0.950 WHIP, and league-leading 128 strikeouts.
Whether a league is scored by points, counting stats or ratios, the amount of innings a pitcher throws magnifies the value of his production. Yes, Verlander was the most valuable fantasy pitcher in 2011 because he led the league in all the traditional categories, but he also threw 251 innings.
Start Verlander not only with confidence of elite innings, but also with a good chance of him pitching eight or nine such innings and staying in long enough to collect the win.
Robinson Cano is irreplaceable because of what he does, relative to his position. This will be an unpopular statement: Cano is the ONLY safe elite second baseman in fantasy baseball... and he's in the midst of his best season yet.
Over the past three seasons, Cano has averaged .314, 27 HR, 104 RBI, 103 runs scored and an .889 OPS. Through half of 2012, he is at .313, with 20 HR, 51 RBI, 57 R, and a .953 OPS.
Now, as for my comment about him being on a tier of his own: Consider the other "elite" second basemen. Ian Kinsler has one season over 150 games in his career and only two over 130, he has also only had over 80 RBI once and batted over .290 only once.
Dustin Pedroia could have been on Cano's level but he is on the disabled list and his 2012 has been marred by injury-damaged production. Jason Kipnis has no track record and his home/road splits are reprehensible (.235/.311/.324 at home, .321/.382/.522 on the road). Brandon Phillips, over his last two full seasons, has hit .287 with an average of 18 HR and 15 SB, good numbers but not elite.
Jose Bautista does not steal bases, nor does he hit for a high average (2011 notwithstanding). But Bautista is simply so powerful, his HR, RBI and inevitable runs scored can provide a significant boost when less balls are flying out of the ballpark than in recent history.
Only 10 players were within 10 home runs of Bautista's league-leading 43 in 2011. So he hit 24 percent more bombs than all but 10 other major leaguers. Bautista's 54 in 2010 were 12 more than anyone else and 15 more than anyone not named Albert Pujols.
Consider that Joey Bats is eligible at third base in most formats, one of the weakest spots on the fantasy diamond, not aided by the extended absence of Evan Longoria, and it is obvious why Bautista's production could be considered irreplaceable.
Don't go crazy! Bryce Harper's production is very much replaceable. But as someone who has played fantasy sports for over a decade now, I have never enjoyed owning a player more. Considering the point of fantasy sports is to have fun (it is, what they call, a game), the fun of owning Harper is irreplaceable.
One does not turn off a National's game when Harper is due up in the next inning, whether they are a Nats fan or not. The excitement of a player who could contribute a walk-off hit, steal of home, or mammoth home run at any moment is, in and of itself, irreplaceable.
Ten catchers have 10 or more home runs in 2012. Six are batting over .280. Four of them are on both of those lists, so why is Buster Posey irreplaceable? Look at the other three.
Carlos Ruiz, before this season, has never had 10 or more home runs, 55 or more RBI or scored 50 or more runs. Yadier Molina has one less home run now than his career high. His average is 28 points over his career .276 mark and his OPS is 138 points over his career mark.
Meanwhile, Posey hit .305 with 18 home runs as the 2010 Rookie of the Year. He was batting .284 with four home runs through 45 games when his 2011 was ended. Now he is 25 years old, batting .289 with 10 home runs. Joe Mauer's injury history and lack of reliable power leaves Posey as the only catcher likely to help you in both average and run production long-term.
One thing most of the players on this list have in common is bankable production. Considering the volatility of Major League Baseball, safety is one of the most valuable commodities for a winning fantasy owner.
Miguel Cabrera has 30-plus HR, 100-plus RBI and .290-plus average since 2004. He has also played in at least 150 games in each of those seasons. He has batted under .320 exactly once since 2005 and has been in the top five in MVP voting five times.
Cabrera would make this list as the first baseman he should be, so getting to use him at third base is simply the cherry on top.
Tim Lincecum is irreplaceable for a different reason. He is undroppable and equally untradeable. There are two schools of thought and no middle ground.
There are those who look at his 9.7 K/9 and say the stuff is still there and he will turn it around any day now. Those people value him as a top-20 starter and will snap him up immediately after you drop him.
The other people look at every other stat of his 2012 and say he is no longer ownable, which guarantees you will not get any value for him on the trade market.
Andrew McCutchen is batting .362, with 18 HR, 60 RBI, 14 SB and 58 R having played 81 games in 2012, or exactly half a season. McCutchen's previous career highs were .286, 23, 89, 33, and 94, but Pirates fans have been telling their friends since his rookie year that this was coming.
The two-time All Star is 25 years old, has already signed an extension through 2017 and is an excellent defensive center fielder, which matters to fantasy owners in leagues where they separate LF/CF/RF (a practice I highly recommend).
McCutchen's career to this point indicates legitimacy in his 2012 breakout, even if the average is boosted by a .407 BABIP (career .324). His speed and athleticism means that number is likely to come down less than most players, and therefore limits the batting average regression. Buy the power and speed and enjoy five-category stardom for years to come.
Mike Trout is 20 years old. He didn't play his first game of 2012 until April 28. He leads the league in stolen bases (26), batting average (.341) and OPS+ (168). He has 12 home runs, 40 RBI and 57 runs scored in 64 games.
Considering the hype on Bryce Harper made him a fashionable late-round pick in many fantasy drafts, Trout was left mostly undrafted, the ultimate waiver wire diamond in the rough. While some may have expected him to have MVP potential in his prime, Trout is a legitimate contender for the award this season, again, at 20 years old.
Trout's skills indicate a player capable of batting well over .300, with 20-plus home runs and 50-plus stolen bases for the next decade. There is no player in baseball like Mike Trout.