The most important player to watch this spring on all 30 teams

AP Photo/Jeff Roberson

Spring training isn't just about getting your arm ready for Opening Day or getting some reps in the cages. For some players, it's a chance to win a job, or keep a job, or prove that you're healthy, or show that you are ready to take the next step. Here are 30 players to watch this spring.

American League

Baltimore Orioles -- Austin Hays, RF. The big story will be Manny Machado moving to shortstop, but I'm not too worried about that transition; he started 43 games there in 2016 and played well (plus-3 defensive runs saved). Hays will be a more interesting guy to watch. A third-round pick in 2016, he jumped all the way from Class A to the majors last year, skipping Triple-A, and the Orioles have apparently handed him a starting job unless he has a terrible spring.

Boston Red Sox -- Tyler Thornburg, RHP. Dustin Pedroia and Eduardo Rodriguez will both be rehabbing from knee surgeries, but remember Thornburg? He had a big season for the Brewers in 2016, the Red Sox traded Travis Shaw (and others) for him, and then he missed the entire season after thoracic outlet surgery.

Chicago White Sox -- Yoan Moncada, 2B. A good approach starts in spring training, and if Moncada is going to maximize his talent, he needs to cut down on the strikeouts. His problem in his first extended stay in the majors wasn't so much chasing out of the zone, but swinging and missing in the zone.

Cleveland Indians -- Michael Brantley, LF. The Indians picked up Brantley's $11 million option even though he had ankle surgery that leaves him questionable for spring training. If the issue persists, the Indians probably will move Jason Kipnis to the outfield and give Yandy Diaz a shot at third base.

Detroit Tigers -- Michael Fulmer, RHP. We want to see if Miguel Cabrera's back is OK, but spring training might not show us much about that. Fulmer had ulnar transposition surgery in September and is expected to be full strength at the start of camp.

Houston Astros -- Anthony Gose, LHP. Yes, that's the former outfielder, trying to make the team as a left-handed reliever. He was a Rule 5 pick so he will have to make the team despite limited mound experience (he pitched just 10 2/3 innings in Class A). It's a flier, but he reportedly touched 100 mph last summer.

Kansas City Royals -- Jorge Soler, OF. The Royals made what looked like a smart trade in acquiring Soler for Wade Davis, but he hit .144 in 35 games and was sent back to Triple-A. He mashed there (.267/.388/.564), but he's 26 now and it's time to produce.

Los Angeles Angels -- Shohei Ohtani, RHP/DH. The Angels' priority will be making sure he's ready for the rotation, but they'll want to give him plenty of time at the plate as well. How they handle him -- and how he hits in the small sample of a few spring games -- will be insight into whether he'll be given a real opportunity as a two-way player.

Minnesota Twins -- Fernando Romero, RHP. With Ervin Santana out until May after finger surgery, there's an opening in the rotation even if the team signs a free agent. Romero or Stephen Gonsalves could break camp with a big spring.

New York Yankees -- Gleyber Torres, 2B/3B. The prized prospect had Tommy John surgery last summer on his non-throwing elbow, but he has been deemed ready to go and the Yankees will give him a long look to see if he can win a job at second base. He has only 55 games above Class A, so a couple of months at Scranton probably still makes sense.

Oakland Athletics -- Dustin Fowler, CF. Called up to the Yankees in late June, he injured his knee slamming into a wall chasing a foul ball -- before he even registered his first big league at-bat. A month later, he was part of the Sonny Gray trade. He has been cleared to play games and could win the center field job.

Seattle Mariners -- Dee Gordon, CF. This is maybe the most interesting position move of the spring as Gordon moves to the outfield. He already has spent much of the offseason tracking down fly balls, but now we'll see how he does in game action.

Tampa Bay Rays -- Brent Honeywell, RHP. Honeywell, No. 15 on Keith Law's top 100 prospects list, struck out 172 in 136 2/3 innings in the upper minors last season. The Rays will certainly game his service time so he'll spend at least a couple of weeks in Triple-A, but a strong spring could prompt a Jake Odorizzi trade.

Texas Rangers -- Willie Calhoun, LF. Nobody doubts his bat after slugging 31 home runs at Triple-A, but the prize for Yu Darvish is transitioning from second base to left field and there are serious concerns how that will go. If he can't hack it, Shin-Soo Choo will have to play more defense in 2018.

Toronto Blue Jays -- Danny Jansen, C. He had never hit until last year, when he started wearing glasses. Boom. He mashed to a .323/.400/.484 line across three levels. The Jays have always liked his defense and, while Russell Martin is signed for two more seasons, a strong impression from Jansen could lead to an in-season promotion.

National League

Arizona Diamondbacks -- Yoshihisa Hirano, RHP. A 34-year-old (in March) veteran free agent from Japan, Hirano throws 90-94 mph with a splitter as his strikeout pitch. Arizona isn't an easy place to pitch, but he'll compete with Archie Bradley and Brad Boxberger to replace Fernando Rodney as closer.

Atlanta Braves -- Dansby Swanson. All eyes will be on rookie Ronald Acuna, but Swanson has a lot to prove after a tough first full season. He struggled against breaking balls, but also hit just .234 against fastballs. Only Alcides Escobar had a lower wOBA against fastballs among qualified batters.

Chicago Cubs -- Kyle Schwarber, LF. He has been working all winter to remake his body. Remember, he did hit .253/.335/.559 in the second half, but the hope is better agility on defense -- without any loss in power.

Cincinnati Reds -- Jesse Winker, LF/RF. Right now, Winker is the fourth man on the outfield depth chart, but scouts have always liked the swing and approach. After never hitting for much power in the minors, Winker suddenly slugged seven home runs in 121 at-bats with the Reds. With his on-base skills, he could beat out Scott Schebler or Adam Duvall for a starting position.

Colorado Rockies -- Jeff Hoffman, RHP. Funny thing about prospects: As soon as they reach the majors and struggle we immediately forget about them and move on to the next shiny toy. While the numbers were scary last year -- not surprisingly, he was especially awful at Coors (7.45 ERA) -- Hoffman has only 130 innings in the majors and he still has the big fastball. Some believe it's too straight and lacks deception, so the off-speed stuff will have to improve.

Los Angeles Dodgers -- Walker Buehler, RHP. Speaking of shiny new toys, Buehler enters spring as Keith's No. 12 prospect and could a win a job as a starter or in the bullpen.

Miami Marlins -- Lewis Brinson, OF. Of all the young players the Marlins received in their trades, Brinson is the one with the biggest tools and most upside. He's pretty much guaranteed to open the season in the big leagues and hopefully he can put his struggles with the Brewers (5-for-47) behind him.

Milwaukee Brewers -- Aaron Wilkerson, RHP. Acquired from the Red Sox for Aaron Hill, Wilkerson was basically an organizational arm before having a big season at Double-A and was pressed into service as a starter in a key game late in the season. He's a finesse guy, but I don't see why he can't beat out Yovani Gallardo for a rotation job.

New York Mets -- Matt Harvey, RHP ... or Noah Syndergaard, RHP ... or Adrian Gonzalez, 1B ... or Dominic Smith, 1B ... or Michael Conforto, OF ... No team has a longer watch list than the Mets.

Philadelphia Phillies -- Vince Velasquez, RHP. Is he a starter? Is he reliever? Can he stay healthy?

Pittsburgh Pirates -- Tyler Glasnow, RHP. At Triple-A, he posted a 1.93 ERA with a 140/32 strikeout/walk ratio in 93 innings. With the Pirates, he posted a 7.69 ERA in 62 innings with a 56/44 strikeout/walk ratio.

St. Louis Cardinals -- Miles Mikolas, RHP. The former big leaguer dominated in Japan the past three seasons, including a 2.25 ERA in 2017, and signed a two-year, $15.5 million contract. He'll be in the rotation, but it will be fascinating to see if he turns into one of the bargains of the winter.

San Diego Padres -- Franchy Cordero, OF. He can open his own Home Depot with all his tools, but the universal appraisal is that he lacks baseball instincts. He had 44 strikeouts and six walks in 99 plate appearances with the Padres last year, but also hit .324/.369/.603 at El Paso (with 18 triples, a line out of the 1930s). The odds are long, but it wouldn't hurt the Padres to give him 400 at-bats in the majors and see what happens.

San Francisco Giants -- Mark Melancon, RHP. He missed much of the second half because of a strained forearm. Given the size of his contract -- he'll make $53 million the next three seasons -- the Giants better hope he can regain his closer stuff.

Washington Nationals -- Adam Eaton, LF. Eaton and Daniel Murphy are both coming off knee surgery -- Eaton tore his ACL in late April and missed the rest of the season -- and both will be eased into spring training. If the knee doesn't respond, Eaton could be pushed by super rookie Victor Robles.