Maybe more than we'd like to admit, injuries play a vital role in the outcome of any season. Deep teams can survive the loss of a single player, but multiple injuries can devastate any team's chances and throw the outcome of their season into doubt. The converse, when a player returns from injury, can be equally uncertain. Injuries can sap skills from a player and returning to the field is no guarantee of returning to pre-injury levels.

This is the issue that now faces a group of players once among the game's best. Their return will influence their team and alter the pennant races. Here are some of the players with the biggest potential impact.

[Much of the information on injuries is taken from the excellent injury database at Baseball Prospectus.]

Josh Beckett
Injury: Thoracic Outlet Syndrome (recovery from surgery). Beckett had surgery to relieve the symptoms; the primary two are numbness in the fingers and hands, resulting in, among other problems, a reduced ability to grip. It's not hard to see how that would negatively impact anyone's ability to conduct a normal day, let alone pitch well.

Prognosis: Beckett had surgery last October. Though he feels better, his recovery is far from certain. St. Louis pitcher Chris Carpenter underwent the same procedure, was able to return to pitching only briefly and subsequently was forced to retire.

2014: Beckett says he feels much better and expects to pitch this season if not by Opening Day. The Dodgers rotation is top heavy with Clayton Kershaw and Zack Greinke, but after that the quality wanes a bit. A healthy Beckett would go a long way toward helping the Dodgers maintain their grip on an increasingly competitive NL West. Betting against Josh Beckett hasn't always been a smart thing to do, but he had declining velocity and declining results for years before this procedure. At least some of that wasn't due to the onset of Thoracic Outlet Syndrome. The guess here is Beckett will be better while he's on the mound, but his ability to stay on the mound will be increasingly suspect. In the end, the Dodgers are going to be glad they signed Paul Maholm.

Michael Pineda
Injury: Torn labrum (shoulder).

Prognosis: A torn labrum is as bad an injury as a pitcher can suffer. There are some success stories, Curt Schilling being perhaps the most prominent, but far more often than not a torn labrum has simply been the last chapter, even if, as in Pineda's case, it was also the first.

2014: Pineda is in Yankees camp, throwing a baseball and saying he feels fine to anyone who will listen. That's already farther than most who suffer the injury get. It's easy to overrate the value of a single player. Baseball seasons are too long and baseball teams are too large for one player to have the kind of impact that, say, a quarterback does in football, or any single player can in basketball. When he was last healthy, Pineda was somewhere between a two- and three-win pitcher, so it's not outrageous to say, with 2012 Michael Pineda in their rotation, the Yankees go from a team on the edge of the playoffs to one in strong position to reach the playoffs. It's easy to hear his words and see his practice pitches and assume Pineda will be there every fifth day for the Yankees, but we heard this same thing last season and then came the set-backs. Torn labrums are the not-so-silent killer of pitchers. For now it looks like Pineda has made it through the storm, but the reality is we're nowhere near being able to know that for sure.

Derek Jeter
Injury: Fractured left ankle (surgery).

Prognosis: The ankle was the primary injury that felled him, but there were other nagging injuries that did their parts as well. According to Jeter himself, he feels great and is 100 percent ready to go, but you didn't expect to hear anything different than that, anyway.

2104: Jeter has always hit. That has never been the problem. His fielding is another matter. Even his staunchest supporters can agree (probably) that a 40-year-old coming off ankle surgery isn't likely to possess much range. For all his greatness, Jeter has never favorably entertained the idea of moving off his beloved shortstop, so unless he can't physically handle the position (more than usual), the Yankees are probably stuck with his defense. The question will be if he can hit enough to make up for what may well be some historically bad defense. Betting against Jeter is bad policy, but betting for 40-year-olds isn't a particularly good idea either. In the end, unless the Yankees are willing to sign Stephen Drew (something they should've done yesterday), they don't have anyone who can replicate Jeter's production at shortstop. That might include Jeter, too. Only 2014 will tell.

Josh Johnson
Injury: Elbow (surgery).

Prognosis: The list of Johnson's injuries covers everything mentioned in the children's song about how bones are connected. ("The knee bone is connected to the… leg bone!" Clearly written by a practicing physician.) Johnson suffered injuries to his elbow, forearm, knee, fingers and triceps, and that was just last season. His performance on the field reflected that list, in that he pitched like a pitcher suffering many ailments simultaneously. Still, hope springs eternal, and never so much as during spring. To wit: Johnson threw 35 pitches off a mound Friday morning and his knee bone remains connected to his ankle bone.

2014: Johnson has always been an injury (or two) waiting to happen. In his nine-year career, he has managed 200 innings just once. Up until last season he had been remarkably productive when on a mound. The Padres are depending on him to move their rotation from adequate to good, and at 30, it stands to reason Johnson could still be 'that guy.' He's lost something on the fastball, but it can still register in the mid-90s. The likelihood is Johnson will be better and still miss time with an injury. He is Josh Johnson after all.

Matt Kemp
Injuries: Shoulder and ankle (surgery).

Prognosis: Kemp is almost the Josh Johnson of outfielders, or at least he has been recently. Hamstring strains, knee contusions, a cartilage injury in his shoulder, surgery for a detached labrum, shoulder inflammation, ankle contusion, ankle surgery and TIME! How'd I do?

2014: Last season Kemp managed only 73 games and, almost worse, his power was gone. This year he's spent the offseason, and will almost surely spend at least part of the regular season, recovering from those ailments while also trying not to create new ones ("No, Matt, please, let me get that firewood. No Matt! NO!!!"). Jokes aside, Kemp is undeniably talented, and if he can regain his health, he is significantly better than Carl Crawford and Andre Ethier, his likely replacements. But right now there is no certainty regarding Kemp's health. He could be the 2011 MVP candidate, the 2013 injury case, or something in between. He was hitting homers in batting practice Friday, which is encouraging in that it's not, not encouraging. For now Kemp will have to remain the wildest of wild cards.

Albert Pujols
Injury: Plantar fasciitis.

Prognosis: Pujols finally tore the plantar fascia, which, while sounding gross, should have the same effect as having had corrective surgery.

2014: Pujols reports his foot, which has bothered him for years before almost completely derailing his 2013 season, is "99.9 percent healthy." That's perhaps the first bit of good news regarding Pujols for Angels fans since his introductory press conference. For the Angels to win in 2014 they'll likely need to overcome their own pitching, and there used to be nobody in the game who you'd want more for that than Albert Pujols. Pujols is 34 now and hasn't had a Pujols! season since 2011. The projection systems, perhaps not aware of his injuries, are bullish, so if he's healthy, maybe hope is justified. Pujols thinks so. The projections think so. With more than $200 million still due on his contract, the Angels sure hope so, too.  

Ryan Braun
Injury: Dumb-dumbness (PED suspension).

Prognosis: Oddly the time missed might have helped Braun, as he was bothered by soreness in his right hand throughout most of the season, causing him to miss 31 games and limiting his prodigious power. There is no indication the injury will linger into the 2014 season, so unlike most everyone else on this list, Braun should be completely healthy and prepared for the season.

2014: Based on the projection systems, the Brewers look to be roughly a .500 team, meaning a couple polite shoves of the needle could result in a playoff berth for Milwaukee. A healthy, productive, not-suspended Ryan Braun represents one, if not more, of those shoves. The only question is whether the time missed will leave Braun rusty but, as he should have all of spring training to get the kinks out, that likely won't be a problem. The guess here is a monster season from Braun is in store.

Ryan Howard
Injury: Knee surgery.

Prognosis: The thing about knees is that once you mess with them, they never quite get back to where they were. However, this is Ryan Howard we're talking about. Speed and quickness aren't exactly his stock in trade. That isn't to say a lingering knee problem wasn't hurting his production last season. Likely it was.

2014: Howard says he's 100 percent healthy and in great shape going into spring training. Of course, he said that last season, too. We may have reached the point in Howard's career when being healthy one day isn't any indication as to whether or not he'll be healthy the next. I wrote last week in this space that, if many things break right for them, there is a chance the Phillies could contend for a playoff spot. Howard being productive is one of those things, though perhaps "break" was a poor choice of words. The time when Howard was an MVP candidate has passed, but a healthy Howard can still be a productive player. As of this writing, he's healthy. He's still healthy now, too. And now. By the time you read this, though, I won't be so sure.