Got to prove yourself every season. That's conventional wisdom, right? Never mind that's it's mostly silly. For a few players, though, some seasons present bona fide challenges.
Here are 20 to keep an eye on this year:
1. CC Sabathia, Yankees: When he began working on a cutter to offset a loss in velocity two years ago, Andy Pettitte said it was a pitch that might just jump-start Sabathia's career. Pettitte also told Sabathia it would take at least a year, perhaps two, to learn. Injuries derailed him after eight starts last season, but if he can stay healthy, the club is hopeful that cutter will help him re-emerge as a productive starter.
2. Justin Verlander, Tigers: He has had a full year to recover from surgery to repair core muscles, and so we'll find out if there's a new normal for this six-time All-Star righty. Don't discount a big comeback season from last season's 4.54 ERA.
3. Joey Votto, Reds: He was quietly piecing together a Hall of Fame resume when a leg injury limited him to 62 games last season. He has passed every test during the offseason, and if he's healthy, the Reds will have taken a huge step back toward contending.
Video: Outlook: Votto could have bounceback year in 2015
4. Jay Bruce, Reds: He had knee surgery in May and probably never fully recovered. At least the Reds hope that's the reason for a huge drop in production. At the ripe old age of 27, he will have the chance to prove the doubters wrong.
5. Bryce Harper, Nationals: Can't help the club in the tub. He has missed 106 games over the past two seasons, and while his teammates appreciate his competitive fire, they also hope he can slow it down a bit and stay on the field. He's only 22 with excellent numbers. He had a 1.251 OPS in 2014, and the Nationals think this just might be a coming-out party of sorts. If he can stay off the disabled list.
6. Ryan Braun, Brewers: He hit .210 in September as the Brewers went 9-17 and let a playoff spot slip away. Afterwards, Braun put the blame squarely on his own shoulders. That wasn't exactly accurate, but it's what the top guy is expected to say. He's hoping an offseason thumb procedure will allow him to again be the player he once was.
7. Mark Trumbo, D-backs: After a frustrating, injury-shortened season, Trumbo is hopeful of again being the guy who averaged 32 home runs for the Angels between 2011-13. If he can settle into the middle of a lineup with Paul Goldschmidt and Yasmany Tomas, the D-backs would have a chance to take big step forward.
Video: Outlook: Trumbo possesses elite power, low average
8. Allen Craig, Red Sox: Foot injuries derailed him the past two seasons. Before that, he was one of the top offensive players in the game. Indications are that he's healthy. If that's the case, Red Sox manager John Farrell will have to find at-bats for him in a lineup that appears set.
9. Nick Swisher, Indians: He hit .208 in 97 games in a season cut short by knee surgery. At 34, Swisher is penciled in to be the designated hitter, and the Indians are hoping there's something left in the tank.
10. Wilmer Flores, Mets: What if he can play? After all the winter speculation about who will play shortstop for the Mets this year, Flores will begin Spring Training as the starter. The club believes he has a chance to be at least an average Major League player, and that would be a huge plus for a team that appears to be of postseason caliber in almost every other area.
11. Alex Rodriguez, Yankees: Can he still be a productive player at age 39 after missing the 2014 season? That's the bottom line. Forget all the other stuff. When we last saw him, he was hitting .120 in the 2013 playoffs. Stay tuned.
12. Pedro Alvarez, Pirates: He has moved from third to first base after last season's throwing problems, and the Pirates are hopeful he can get back to being the 30-home runs, 20-doubles player he was in 2012 and '13. He's only 28.
Video: Outlook: Rollins offers speed and power at shortstop
13. Jimmy Rollins, Dodgers: He was once one of the most dynamic players in the game and a leader in all the good ways that word is used. He's 36 and the Dodgers are hoping a change of scenery will be the perfect tonic to restart his career.
14. Tim Lincecum, Giants: There have been occasional flashes of greatness the past three seasons. Mostly, though, he has been a shadow of the guy who made the game look so easy from 2008-11. The Giants again have him penciled into their rotation, but they've added enough depth that they're not dependent on him.
15. Will Middlebrooks, Padres: Around this time last season, a lot of people were predicting a huge breakout season for the third baseman. Injuries and a lack of production ended his tenure in Boston, so he's getting a new start with the rejuvenated Padres. At 26, he needs to show both that he can stay healthy and that he's not the .213 hitter he has been the past two seasons.
16. B.J. Upton, Braves: He's trying anew to resurrect his career after hitting .198 during two seasons in Atlanta. The Braves don't know what to expect, but they haven't forgotten that he was once one of the guys who made the Rays go during some very good years.
Video: Gonzalez on Hamilton's injury, Joyce's importance
17. Josh Hamilton, Angels: Is it the injuries or the lack of plate discipline? In two seasons with the Angels, he has not come close to resembling the guy who played in five straight All-Star Games for the Rangers. He'll begin Spring Training recovering from shoulder surgery. The Angels have no idea when he'll be back on the field or how well he'll play.
18. Ubaldo Jimenez, Orioles: He has reworked his delivery after a season in which he had a 4.81 ERA. With three seasons remaining on his contract, he'll have plenty of chances to get back on track.
19. Elvis Andrus, Rangers: There was a time when he seemed on his way to becoming an elite shortstop. At 26, he still may be that guy. The Rangers say he has worked relentlessly this offseason to get in shape and to try again to be the player the club once projected him to be.
20. Jon Singleton, Astros: The Astros were so sure he was going to be a star that he got a $10 million contract before he'd gotten a real taste of the big leagues. After hitting .168, he'll have to win a job in Spring Training. He's just 23 and the Astros continue to say all the right things. But they have other options if he doesn't have a good spring.
Richard Justice is a columnist for MLB.com. Read his blog, Justice4U.