PHOENIX -- Mookie Betts in 2016.
Bryce Harper in 2015.
Players break out all the time, and this year will be no different.
Naming names is the most difficult part.
Maybe it a player returning to form from an injury. Medical science and the latest rehabilitation tools are remarkable things.
Or a prospect turning his strong initial showing into an everyday occurrence.
Who has adjusted his hitting approach in the offseason?
Who has added or perfected another pitch?
We will find out soon enough. Here is a look at the spring training player to watch for all 30 teams.
AMERICAN LEAGUE WEST
Carlos Beltran made his bones in his first stint in Houston in 2004, when he helped the Astros to the NL playoffs after being acquired from Kansas City in June. Beltran made his money after hitting eight postseason homers, signing a seven-year, $119 million deal with the Mets. He returns to the Astros to help fuel another playoff run.
Cameron Maybin is the kind of player who could flourish in Mike Scioscia's system. Maybin recorded 40, 26 and 23 stolen bases in the three seasons in which he played at least 125 games, and Scioscia likes little ball. Maybin slashed a career-high .315/.383/.418 in 94 games with Detroit last year.
Sonny Gray's forearm injury not only limited him to 22 starts and caused a career-high 5.69 ERA last year, but it also deprived the A's of their most dependable starting pitcher. Oakland used 14 starters last year, all of whom made at least five starts. Gray is healthy now, and the A's need him.
Since his 19-win 2009 season, Felix Hernandez has been ridden hard and put away wet. Is it catching up to him. He averaged more than 226 innings in the next six seasons after that before a 2016 calf injury limited him to 25 starts, 153 innings and a 3.82 ERA, his highest mark in a decade. How will be recover?
Jonathan Lucroy identified the Rangers as the best fit for his present and future at the trade deadline last July when he refused a trade to Cleveland, and he was right in the short term, producing 11 homers, 31 RBIs, a .885 OPS in 47 games with the Rangers. His presence all year will be another plus.
AMERICAN LEAGUE CENTRAL
Left-hander Jose Quintana has become the de facto ace of the staff after Chris Sale's departure, and he deserves it. Quintana has not missed a start in four years, and he owns a 3.35 ERA and a 1.22 WHIP in that span, good numbers that look even better a hitter's park. It is no wonder teams are after him.
Carlos Carrasco really is not fair. His four-pitch mix begins with a 94 mph fastball and includes a slider that according to Fangraphs was one of top eight pitches in getting swinging strikes and ground balls. Terry Francona's brilliant postseason use of Andrew Miller masked Carrasco's absence because of a fractured hand, but Carrasco is healthy again.
Wife Kate Upton was right, Justin Verlander was cheated out of the 2016 AL Cy Young Award after a 16-win, 254-strikeout season. Verlander, who turns 34 on Feb. 20, remains the ace of a staff that needs everything it can get out of him. He has subtly changed his repertoire with a little more slider and a little changeup.
The Royals had success in resurrecting Kendrys Morales' career, and now they are betting on the upside of Jorge Soler. The right fielder was acquired from the Cubs over the winter for 2018 free-agent-to-be Wade Davis, one of those offseason deals small-market clubs must make. Soler homered once every 19 at-bats last year.
Top prospect Byron Buxton, the 2012 No. 2 overall draft pick, has yet to make the splash scouts predicted, which goes to the perils of scouting and the difficulty of the game at the highest level. However, Buxton's power/speed tools have not gone away, and he may be poised to break out in his age-23 season.
AMERICAN LEAGUE EAST
Mark Trumbo hit a major-league-high 47 homers last year in a park that suited him perfectly, and it seemed like the perfect jumping off point into free agency. The market did not respond, leaving him little choice but to return for $37.5 million over three years. How will he respond?
Pablo Sandoval is penciled in as the Red Sox's starting third baseman entering spring training. Yes, that Sandoval, the one who disappointed in 2015 after signing a five-year, $95 million free agent deal and then missed almost all of last year with a shoulder injury. On the positive side, he can hit, and he is reported to be in shape.
Catcher Gary Sanchez blew up after being promoted in early August, hitting 11 homers in a 15-game span and 20 homers in 53 games overall. The Yankees believe in him, trading Brian McCann in the offseason, and Sanchez worked on his strength during the winter in order to sustain over a full season.
Matt Duffy was a stealth star in San Francisco's 2014 World Series win, flashing power and a plus glove at third base while finishing second in the Rookie of the Year voting. The principal return for Matt Moore at last year's deadline, Duffy should fit at shortstop, where he spent most of his minor league career.
Put Devon Travis's first two injury-hampered seasons together and you have a very workable second baseman -- 46 doubles, 19 homers and 85 RBIs in 163 games. Shoulder and issues limited him 2015-16, and he was forced out of the AL Championship Series with a knee injury. Healthy, he enters spring as the top choice to hit leadoff.
NATIONAL LEAGUE WEST
The D-backs opted to scapegoat general manager Dave Stewart and manager Chip Hale for their 2016 struggles, but the late spring injury to A.J. Pollock was the more appropriate culprit. A two-way producer who ranked sixth in the majors in WAR in 2015, Pollock is back after playing only 12 games last year.
Rookie shortstop Trevor Story was a walking history lesson last year, tying major league records with 10 homers in April and 10 homers in his first 21 games. Thumb surgery cost him the final two months of the season after he hit 27 dingers in 97 games. He is healthy again, but that will be a tough act to follow.
Justin Turner knew exactly how to handle a contract year, setting career marks in virtually every offensive category -- 34 doubles, 27 homers, 90 RBIs -- in his first season as a regular. The Dodgers have to algorithms to believe he can do it again, and they gave him a four-year, $64 million deal as proof.
The most intriguing name in a mostly retread rotation is right-hander Luis Perdomo, who was thrown into the fire in his age-23 season after joining the Padres in a roundabout Rule 5 move. He throws 94 mph and showed progress after moving into the rotation for good in mid-June.
Hunter Pence missed only two games from 2012-14 before injuries limited him the past two seasons. The Giants are solid on offense but not particularly overpowering, and they need Pence's middle-of-the-order bat to be at their best. At 33, it remains to be seen if injuries will persist.
NATIONAL LEAGUE CENTRAL
Kyle Schwarber was the feel-good story of the World Series when he returned from a devastating leg injury in time to serve as a designated hitter in the games at Cleveland. Schwarber brings another big bat to a talented roster and another malleable piece for manager Joe Maddon.
A starter in 2015, Cuban free agent Raisel Iglesias was used out in the bullpen when he returned from injury last June after missing two months. He converted six of eight save opportunities when asked to close in August, and he has the stuff to keep the role.
Right-hander Zach Davies is not physically overpowering at 6 feet, 155 pounds, and his fastball rarely passes 90 mph. However, he has extraordinary command of a four-pitch mix -- the best command in baseball in 2016, according to Baseball Prospectus. He could be ready to take another step up the rotation.
Right fielder Gregory Polanco is so athletic -- 6-foot-5, 235 pounds -- it is scary, and he put it all to use in a breakout 2016 season with 34 doubles, 22 homers, 86 RBIs and 17 stolen bases in his age-24 season. A 30-30 season and superstardom await.
Right-hander Michael Wacha is the Cardinals' nominal No. 5 starter for now, and he has the resume to validate his choice after a 17-victory 2015, his only healthy season in the past three. However, top prospect Alex Reyes is waiting in the wings, and it may be only a matter of time ...
NATIONAL LEAGUE EAST
Shortstop Dansby Swanson was everything Atlanta believed he would be in his first dip in the major league pool last season, slashing .302/.361/.442 with seven doubles and three homers in 38 games after an August promotion. The first overall pick in the 2015 has All-Star written all over him.
Right-hander Dan Straily was solid in an under-the-radar manner after the 2016 All-Star break. He won eight of his last 10 decisions and gave up more than three runs only once in 15 second-half starts. On the season, he allowed three or fewer hits in 11 starts, tied for the major league lead.
Jose Reyes rehabilitated himself after rejoining the Mets following a two-month suspension last summer, hitting eight homers and stealing nine bases in 60 games. But he played third base, and David Wright is back after missing the better part of two seasons with back issues. How will that play out?
Shortstop Freddy Galvis was a power hitter and a plus defender in his second season as a regular in 2016, when he hit 20 homers, equaling the number from his first four seasons combined. Which begs the question, what do the Phils do when J.P. Crawford, Baseball America's No. 1 minor league prospect, is promoted?
Shortstop Trea Turner was a revelation after an early-June promotion last season, and his acquisition as the player to be named in a three-team trade finalized in June 2015 could rank as GM Mike Rizzo's finest deal. Turner amassed 13 homers, 33 stolen bases and a .937 OPS in 73 games. Scary good.