The Yankees have not had great luck with injuries these past few seasons. No team can completely avoid injuries, but they seem to attract the injury bug more than most.
In 2013, the roster combined to spend around 1,500 days on the disabled list, the third most in baseball. Alex Rodriguez, Mark Teixeira, Curtis Granderson, Derek Jeter and others all missed a significant amount of time. In 2014, Teixeira, Masahiro Tanaka, Carlos Beltran and Michael Pineda all missed large chunks of time. Last season, Teixeira again, Jacoby Ellsbury, Andrew Miller, and multiple starting pitchers landed on the DL.
This season figures to be more of the same. Many Yankees have a history of injury problems and/or are aging, meaning they're more vulnerable to injuries. Despite the Yankees (seemingly successful) youth movement and "rebuild," this season still largely hinges on the health and production of older, injury prone players.
The Yankees and their fans would love if everyone could stay healthy, and while we obviously don't root for anyone to get hurt, there are some guys that we really don't want to get hurt. The team would seriously be weakened if the players below missed any signicant time..
Teixeira tops the list for a few reasons. First off, he's just a really good player, and when teams' really good players get hurt, it's not good (#analysis). Secondly, his switch-hitting bat gives the lineup a great deal of balance. The lineup is lefty-heavy with Ellsbury, Brett Gardner, Brian McCann, and Didi Gregorius all being true lefties.
The addition of Starlin Castro will help somewhat balance the lineup, but A-Rod is still the Yankees' only right-handed power bat. Beltran hasn't been productive from the right-side of the plate as he's aged, and Chase Headley has just 12 home runs batting righty over the past three seasons. When Teixeira is out, the Yankees struggle against lefties (see September and the AL Wild Game).
Lastly, but just as important, the Yankees have a severe lack of depth at first base in wake of the Greg Bird injury. Dustin Ackley figures to be the primary backup, but he's played a whopping 22 games at first in his career. After that, it's likely going to be Chris Parmelee, who is better suited as a Triple-A player than as the first baseman of the New York Yankees.
Teixeira may not be their "best" player, but it's hard to argue that he's not their most important. Last season, the Yankees were 65-52 on August 17th, averaging 4.8 runs per game. That day, Teixeira fouled a ball off his right leg, fracturing it and causing him to miss the rest of the season outside of a few at-bats he probably shouldn't have had. Greg Bird's surge certainly helped, but the lineup wasn't the the same with a lefty instead of the switch-hitting Teixeira.
After Teixeira's injury, the Yankees went 22-23 and averaged 4.6 runs per game before getting shut out to the Astros in the Wild Card Game. Teixeira hasn't exactly been the picture of health these past few seasons, but it's clear the Yankees need him.
It's probably not a good sign that the guys the Yankees most need to stay healthy are also the most likely to get hurt, but such is life. Tanaka's right elbow has been and will continue be a source of heartburn for Yankee fans. Any pitch could be the one that triggers Tommy John, but hopefully he'll be able to have his first full year in pinstripes in 2016.
When healthy, Tanaka is an innings-eating ace. He's averaged almost seven innings per start to an ERA of 3.16 over these past two seasons. He has a bit of a home run problem, but with his nasty stuff and control, he's the Yankees' best starter. The rest of the rotation is filled with question marks. Michael Pineda's peripherals continue to suggest a breakout, but we keep waiting. Nathan Eovaldi looked great in the second half before landing on the DL, but he's not a sure thing. Luis Severino looks like a stud, but a sophomore slump isn't out of the question. CC Sabathia just isn't good anymore, and Ivan Nova is completely unpredictable.
So, while the Yankees do have five proven starters behind Tanaka, there's not a ton of depth in the minors, and he is the only one who can consistently eat innings. No team wants to lose their ace, but a team with as many rotation question marks as the Yankees especially can't afford it.
The shortstop started off slow last year, but had a .294/.345/.417 second half slash after acclimating to pinstripes. Gregorius is about to enter what should be the prime of his career, so expecting something around there or more isn't a stretch, and that's great for a middle infielder, especially when they play defense as will as Sir Didi does. FanGraphs ranked him the best defensive shortstop in the American League last season. He also had the fourth highest fWAR of all shortstops. So Gregorius is already a top-five shortstop in baseball, and he'll only get better.
Another reason he's so important is the lack of infield depth the Yankees have. The only middle infielders the Yankees have listed on the 40-man roster are Gregorius, Castro, Rob Refsnyder, and Ronald Torreyes. If Gregorius goes down, Castro could shift to short, Refsnyder starts at second and Torreyes and Ackley could play roles as backups, but that isn't exactly pretty.
Dellin Betances- One could make the argument he's the Yankees' best player, but because of Andrew Miller and Aroldis Chapman, he's likely not as vital as the other guys listed. That being said, if Betances misses any time during Chapman's 30-game suspension, then it could get scary.
Brian McCann- The lefty slugged 26 homers last year, and while his absence would cause a hole in the lineup, they would badly miss McCann behind the plate; he has a sterling defensive reputation. As talented as Gary Sanchez is, rookies offer no guarantees, and there would be a learning curve for the pitchers to get used to throwing to him.
Chase Headley- Not that special, but there is absolutely no third base depth right now. Starlin Castro and Rob Refsnyder are taking grounders there to potentially be backup options, and they have never played there in their lives. If Headley misses time, the Yankees go from slightly above replacement level to way below with the likes of Pete Kozma or Donovan Solano. Yeesh.
Alex Rodriguez- He's the only righty power bat they have and was great last season, but because A-Rod's strictly a DH, his value goes down.
Luis Severino- We would cry.
Every player on the roster plays their own important role, but the people listed above are more valuable than others due to their talent, and the questionable depth behind them. So Teixeira, Tanaka, Gregorius... please don't get hurt.