Every MLB team's X-factor for the 2020 season

Arizona acquired Gallen from Miami for top shortstop prospect Jazz Chisholm at last year's trade deadline, but the D-backs knew what they were getting into. The right-hander had a breakout season, including a 2.81 ERA in 15 starts between the Marlins and Diamondbacks. If he can continue to be a No. 1 starter, Arizona has a chance to compete for a wild-card spot.

Riley took MLB by storm last year with 14 home runs in his first six weeks in the majors, but his inability to make contact eventually caught up to him. The Braves lost Josh Donaldson in the offseason and desperately need someone to pick up the slack offensively. Riley has shown he can be the answer for the reigning NL East champs, but he needs to make adjustments.

Mountcastle has yet to make his MLB debut, but he's the most exciting prospect the rebuilding O's have in the upper minors. Drafted as a shortstop, Mountcastle has moved over to first base and is limited defensively, but he hit .312-25-83 in 553 plate appearances at Triple-A in 2019. After a few weeks in the minors, he's likely to see regular playing time for Baltimore.

Boston's starting rotation is in shambles after trading David Price and experiencing Chris Sale's elbow injury setback. The Sox need their remaining starters to pitch to their potential, particularly Eovaldi. He threw only 67.2 innings last year after signing a four-year, $68 million extension, but Eovaldi remains one of the hardest throwers in the game. To have any chance at remaining competitive this year, Boston needs Eovaldi to stay healthy.

Kimbrel signed a three-year, $43 million contract well into last season, but he was terrible when he arrived as Chicago's new closer and missed time late due to injuries. He's been the best reliever in baseball during multiple seasons of his career, and after losing Steve Cishek, Pedro Strop and Brandon Kintzler, the Cubs lack many viable alternatives should Kimbrel continue to struggle.

The 22-year-old Robert was one of the most exciting prospects in the game before Chicago signed him to an extension this offseason, effectively giving the Cuban outfielder a chance to break camp with the team. He hit .328-32-92 with 36 steals in 122 games between three levels last season and could add even more excitement to one of the most active teams in baseball this offseason.

Bauer was a favorite to win the AL Cy Young in 2018 with Cleveland before a fluke leg injury ended his season. Last year didn't go nearly as well, especially after the enigmatic right-hander was traded to Cincinnati at the deadline. The Reds know he's capable, with a K/9 of at least 10.0 in three straight seasons, and the team has a chance to make some noise this season if Bauer pitches like he's capable of doing.

Reyes has tape measure power and launched 37 home runs last year, his first full season in the majors. He gave Cleveland a spark late in the year after getting traded from San Diego, and he will be an important middle-of-the-order hitter for a team that struggled offensively at times last year. If Reyes can spark the offense, Cleveland's excellent starting pitching, led by Shane Bieber, should take care of itself.

Colorado's pitching had a complete downfall last year, and Marquez was at the center of that decline. The ace's ERA increased nearly a full run from 2018 to 4.76, and he missed time due to injury. The good news is that his control remained elite, and the right-hander also continued to fan more than one batter per inning. It will take a lot to go right for the Rockies to return to the playoffs, and Marquez is at the top of the list.

The rebuilding Tigers are loaded with minor league pitching talent, but their hitters are few and far between, especially in the upper minors. Stewart has already arrived, and despite a disappointing rookie season, he could be in a position to make a difference soon. He hit at least 25 home runs three times in the minors and has the talent to be a capable middle-of-the-order hitter if he can put it together.

McCullers missed all of 2019 due to Tommy John surgery, but he's arrived to spring training healthy. During his four years of performance, McCullers has a 3.67 ERA and 10.1 K/9. Injuries have been a major issue holding him back, but if he can stay healthy, McCullers could help Houston fill the void left by Gerrit Cole.

Mondesi is K.C.'s most exciting player, if not the most exciting player in MLB when he's healthy. Unfortunately, he was able to play only 102 games last season due to injury, but even during that time he has 39 extra-base hits and he swiped 43 bases. The shortstop is also a wizard defensively and gives Royals fans reason to show up to Kauffman Stadium despite a likely mediocre team performance.

Ohtani is one of the most unique talents MLB has ever seen, with the ability to be a top player as a hitter and a pitcher. He will continue to serve as the Angels DH at the beginning of 2020 and could return from Tommy John surgery to pitch in the starting rotation by mid-May. If he can stay on the field, Ohtani could compete for AL MVP alongside teammate Mike Trout.

May showed why he was a top prospect after the Dodgers promoted him last year. While he's expected to start the season in the minors, May will remain a starting pitcher this season and it shouldn't be long before he's back in L.A. Behind Walker Buehler, Clayton Kershaw, David Price and Julio Urias, May gives the Dodgers a lethal starting rotation.

Villar was effectively sold off by the Orioles in an early December trade due to his salary, but the Marlins happily took him. One of last year's most exciting players, Villar had 24 home runs and 40 steals as a regular for Baltimore last season. He will try to bring his spark to Miami this year, where he will likely begin the season at third base but should play all over the field.

Peralta has struggled to find consistency as a swingman in his first two seasons, but the upside looked tremendous with 11.6 K/9 in his career. The right-hander hides the ball extremely well and has a fastball that jumps out of his hand. Milwaukee apparently believes in the potential, signing Peralta to a contract extension this spring.

Arraez stole the second base job away from Jonathan Schoop last year and is set to be the starter and possible leadoff man this season. He's a unique player in today's MLB, with an elite contact rate and line drive rate, a combo that could win him a batting title sooner than later. He posted an outstanding .399 on-base percentage last season and could be a perfect complement within the Twins powerful lineup.

Cespedes played only 38 games in 2018 and didn't appear in a game last year due to injuries. The Mets are relieved to see him healthy this spring, making an outfield that was already deep even deeper. It's hard for the team to count on him, but Cespedes has the power to put the offense over the top if he does prove to be healthy.

The Yankees signed Gerrit Cole in the offseason, but they've already lost Luis Severino for all of 2020 and James Paxton for at least the first few weeks of the year. Those injuries opened up a rotation spot for Montgomery, who is returning from Tommy John surgery. The lefty has a solid 3.91 ERA for his career and is capable of holding down the fort while the rest of his teammates are on the mend.

Oakland couldn't be more excited about Luzardo, who is set to break camp in the starting rotation. The top prospect threw only 43 innings in the minors last year due to injury, but he's been nothing but dominant in the time that he has pitched as a pro. Lining up behind Sean Manaea and Frankie Montas in the rotation, Luzardo should help make the A's a contender again in 2020.

The depth of Philadelphia's bullpen was a problem last year, mostly due to injuries. Dominguez was one of the more costly injuries, as the hard thrower who served as closer for much of 2018 was able to make only 27 appearances last season. The Phillies are relying on Dominguez to stay healthy this year to set up Hector Neris, and the team doesn't have many great alternatives for that role.

Hindered by a shoulder injury, Polanco appeared in only 42 games for the Pirates last season. That followed a breakout 2018 season in which he hit 23 home runs with an .839 OPS. He's been healthy this spring, and the pressure will be on Polanco to be a middle-of-the-order hitter after the Pirates traded Starling Marte.

The Padres have seen several top prospects arrive over the last year, and Gore is next. The lefty had an incredible 2019 season between High-A and Double-A with a 1.69 ERA and 12.0 K/9 in 20 starts. San Diego showed its aggressiveness in pushing prospects with Fernando Tatis Jr. and Chris Paddack last year, and Gore could be set to make a big impact by the All-Star break, if not sooner.

Posey has struggled over the last two seasons due to a hip injury, but he's arrived to spring training healthy more than a full year removed from surgery. The former Rookie of the Year and MVP can't be expected to be the player he used to be now at age 33, but he can go a long way to improving the weak Giants offense if he can rebound somewhat.

Long is competing this spring not only for the starting second base job but also for the leadoff role. He played well during his brief rookie season, posting a .787 OPS in 42 games, and has shown an interesting combo of power and speed. With the Mariners rebuilding, Long is one of the few players currently on the roster who could be there to stay for the long term.

The Cardinals allowed Marcell Ozuna to walk in free agency and didn't add a replacement. Part of the reason is likely due to Carlson's readiness for the majors. The top prospect is off to a hot start this spring after hitting .292-26-68 with 20 steals between Double- and Triple-A last year, and he is doing everything he can to make the opening day roster. The Cardinals desperately need an offensive spark after Paul Goldschmidt and Matt Carpenter declined last year.

The Rays have a deep starting rotation, but it's already being tested by Blake Snell's early spring elbow issue. McKay struggled in the majors last year, with a 5.14 ERA in 49 innings, but the peripherals (3.50 K/BB, 10.3 K/9) and a great minor league track record show immediate upside. Currently the team's sixth starter, McKay could play a huge role in 2020.

As they open their new ballpark, the Rangers have revamped their starting rotation with Kluber, Kyle Gibson and Jordan Lyles. Despite his two Cy Young Awards, it's difficult to know what to expect from Kluber in 2020 after he lost velocity and made only seven starts last season due to injuries. If Kluber is back in Cy Young form, the Rangers could be a surprise team this season.

Arguably the top prospect in baseball when he was promoted last year, Guerrero Jr. disappointed by hitting .272-15-69 in 514 plate appearances. He still stung the ball regularly, and even his rookie performance was impressive given that he was just age 20. Toronto will have a difficult time competing in the AL East this year, but Guerrero Jr. could speed up the team's timeline if he shows star ability.

The defending World Series champs took a sizable loss with Anthony Rendon going to the Angels in free agency. Washington decided to replace him from within, bringing back Asdrubal Cabrera and hoping that Kieboom could emerge this season. The top prospect struggled during his MLB debut last year, but he posted a .902 OPS at Triple-A.