While teams enter each season with a plan and some expectations for how the year will go, not everything can be forecasted. At some point, every club has to lean into the unknown and hope for the best.

Below, you’ll find each team's Great Unknown for the 2019 season. Each player has a wide range of potential outcomes and could make a major difference in how the upcoming campaign plays out.

AL EAST

Blue Jays: RHP Aaron Sanchez

Sanchez went 15-2 with an AL best 3.00 ERA in 2016, but the last two seasons have been a struggle with injury after injury. At his best, Sanchez is a Cy Young Award contender. At his worst, Sanchez scatters his fastball and gives up too many home runs. He is the epitome of the Great Unknown. More >

Orioles: 1B Chris Davis

What to do with Davis? And how will the Orioles’ new regime react if he slumps again, after Davis put up arguably the worst offensive season in Major League history in 2018? The upwards of $92 million he’s still owed through 2022 looms over the organization’s every decision. More >

Rays: OF Avisail Garcia

Garcia, who was non-tendered by the White Sox in November before signing with the Rays, saw his production decline significantly in 2018. He went from hitting .330 with a .885 OPS in '17 to finishing with just a .719 OPS a year ago. The 27-year-old believes knee issues played a big role in his struggles, however, and Tampa Bay is hoping that turns out to be the case. More >

Red Sox: 2B Dustin Pedroia

After dealing with left knee problems over the past two years, Pedroia has shown encouraging signs this spring. But until Pedroia engages in the grind of the regular season, it will remain unclear if he can play unencumbered and return to his previous level of production. More >

Yankees: SS Troy Tulowitzki

With Didi Gregorius sidelined as he recovers from Tommy John surgery, the Yankees are counting on Tulowitzki to rebound after playing just 66 games in 2017 and missing all of last season due to injuries to both heels and his right ankle. The version of Tulowitzki who appeared on five NL All-Star teams with the Rockies between 2010-15 and won a pair of Silver Sluggers and Gold Gloves, would be a fantastic addition for New York. More >

AL CENTRAL

Indians: OF Carlos Gonzalez

The Tribe signed Gonzalez to a Minor League deal on Tuesday, but he has a few things to prove before he gets slotted into either of Cleveland’s corner outfield spots. Because he’s missed virtually all of Spring Training, he has until his April 20 opt-out date to get himself game-ready. The big uncertainty that comes with the former Rockie is if he’ll be able to find offense success without the thin air at Coors Field. If he can, the Indians' outfield could improve greatly. More >

Royals: LHP Danny Duffy

Duffy signed a five-year, $65 million deal after a superb 2016 season as the Royals were certain they locked up an emerging ace to a long-term deal. But injuries have plagued Duffy since, and his ERA in 2018 (4.88) was his worst since his rookie year in 2011. And his season was cut short. Once again, Duffy this spring is trying to fight through injury. He could be back from shoulder tightness sometime in mid-April. But just how much will Duffy give the Royals in 2019? More >

Tigers: 1B Miguel Cabrera

For all their young talent, the Tigers will go as far in 2019 as Cabrera and his 35-year-old body can carry them. If he’s healthy, Detroit’s offense can click around him, and the Tigers should exceed expectations. If injuries hound him again, the lineup has a massive hole. More >

Twins: OF Byron Buxton, 3B Miguel Sano

Buxton and Sano have flashed glimpses of their tantalizing potential, but they've been unable to sustain it on the field. At their best, Buxton's five-tool talent and Sano's 30-homer power could anchor a playoff team, but Buxton struggled with injuries and underperformance last season while Sano worked to get his conditioning on track. This year, Buxton is back with a simplified swing and Sano is in noticeably better condition as the Twins enter a pivotal season for their two young stars. More >

White Sox: RHP Dylan Cease

Cease, who was acquired from the Cubs alongside Eloy Jimenez and two other Minor Leaguers for Jose Quintana in 2017, is a major part of the White Sox rebuilding plan. The right-hander hasn’t advanced past Double-A yet, but he was named the 2018 Minor League Pitcher of the Year by MLB Pipeline and should make his MLB debut this season. What’s unknown is when that debut will come and what his innings limit will be. More >

AL WEST

A’s: RHP Marco Estrada

The A's locked up Estrada for the season and hope the veteran starter has a bounce-back performance in him after posting a career-worst 5.64 ERA with the Blue Jays in 2018. The former All-Star, who has been prone to the long ball, should benefit from pitching in the Coliseum, and the A's badly need innings from him in a rather weak rotation. More >

Angels: DH Shohei Ohtani

Ohtani proved he's an elite talent as both a hitter and a pitcher while winning AL Rookie of the Year honors in 2018, but he'll now have the new challenge of being an everyday designated hitter once he returns in early May from Tommy John surgery. More >

Astros: LHP Wade Miley

The Astros are hoping Miley, who was rocked for a 5.48 ERA and a 1.57 WHIP over 2016-17 with the Mariners and Orioles, can continue his late-career resurgence and give them another steady arm in the bullpen. He was terrific last year with the Brewers, and the Astros believe it’s not a fluke. More >

Mariners: LHP Yusei Kikuchi

Kikuchi, Seattle’s latest Japanese addition, looked impressive in his first start against the A’s on Thursday in Tokyo. But as with any rookie, there’ll be questions as he faces the long haul of a Major League season. And for the 27-year-old, there are the added challenges of adjusting to a new style of play, a new country and a whole a new way of life. Early signs are positive as Kikuchi has proven to be an eager and quick learner in Mariners camp. More >

Rangers: RHP Shelby Miller, RHP Edinson Volquez, LHP Drew Smyly

The Rangers’ Tommy John experiment is about to begin. Texas’ rotation is depending heavily on Miller, Volquez and Smyly, who each underwent reconstructive elbow surgery in 2017. Volquez and Smyly missed all of 2018, while Miller threw just 16 innings and posted a 10.69 ERA for the D-backs. More >

NL EAST

Braves: LHP Sean Newcomb

Newcomb’s fastball, deceptive left-handed delivery and big, athletic frame helped him become one of baseball's top pitching prospects. But the 25-year-old southpaw has remained a bit suspect as he has produced a 4.06 ERA while walking 12 percent of the batters he's faced through his first 49 career starts. He has the potential to establish himself as a front-line starter or possibly find himself back at the Minor League level this year. More >

Marlins: OF Lewis Brinson

Brinson started off Spring Training hot, but has cooled off toward the end of camp. What's encouraging to the Marlins is the quality of the 24-year-old's at-bats have improved all spring. He's expected to open the season in center field, and he may wind up being a middle-of-the-order presence. More >

Mets: SS Amed Rosario

In the second half of 2018, Rosario began making good on his status as the former No. 2 prospect in baseball. Entering 2019, the Mets are again counting on Rosario to be a key member of their team. But what is Rosario? An All-Star caliber player with an uncommon mix of power and speed, or a placeholder until the next generation of shortstops arrives? More >

Nationals: OF Adam Eaton

When Eaton has been on the field, fans have seen glimpses, albeit brief, of the kind of impact player the Nationals believe they acquired from the White Sox two winters ago. And all throughout Spring Training, the Nationals are beginning to see that player once again. Eaton appears fully healthy, not hampered by the lingering effects of the torn ACL in his left knee from April 2017 or the ankle injury from the same day that required arthroscopic surgery last May. He has played in 15 Grapefruit League games this spring, about the same as the rest of the Nats’ starters, and has done so uninhibited or without requiring much extra maintenance. More >

Phillies: OF Odubel Herrera

Herrera was one of the game’s better players from 2015-17, posting a combined 10.5 WAR, according to Baseball-Reference. But he posted a career-low 0.2 WAR last season, putting him on notice. Herrera must focus and produce consistently to remain in the Phillies’ lineup in 2019. If he does, the Phillies’ lineup could be pretty dangerous. If he does not, then look for Roman Quinn or Aaron Altherr to get playing time in center field. More >

NL CENTRAL

Brewers: RHP Jimmy Nelson

Nelson flashed ace potential in 2017, posting a 3.49 ERA with 199 strikeouts in 175 1/3 innings, but he hasn’t pitched for the Brewers since undergoing right shoulder surgery in September of that season. The right-hander was thought to be close to a return, but he received a cortisone shot Friday after experiencing right elbow soreness, which may further extend his timeline. More >

Cardinals: RHP Alex Reyes

Reyes has been ranked as the Cardinals’ top prospect in four consecutive seasons, but he has spent the past two years rehabbing -- first from Tommy John surgery and then from surgery to repair a tendon attached to his right lat muscle. The phenom is now healthy and could eventually end up in St. Louis’ rotation, though he’ll open the year in the bullpen. More >

Cubs: RHP Yu Darvish

Two winters ago, the Cubs reeled in Darvish with a six-year, $126 million contract, adding what they thought would be a valuable impact arm to the rotation. Instead, injury issues ended Darvish's season in 2018 after only eight starts. The righty arrived to Spring Training healthy and firing 96 mph fastballs with regularity. Darvish has looked strong and has oozed comfort and confidence, conducting interviews in English and showing off his sense of humor. If Darvish lives up to what the Cubs have seen this spring, he could be key in helping the team's veteran-laden rotation guide the club back to the top of the NL Central. More >

Pirates: 3B Jung Ho Kang

The Pirates have only seen Kang play three Major League games since 2016, as he could not enter the United States in 2017 and early ’18 after a DUI arrest in his native South Korea, yet they are trusting him to be their starting third baseman based on the power potential he displayed in 2015-16 and the physical fitness he’s shown this spring. Club officials have openly referred to him as a “wild card.” The soon-to-be 32-year-old could struggle after spending so much time away from the game, or he could erase some of the uncertainty surrounding Pittsburgh’s lineup and infield defense. More >

Reds: INF/OF Nick Senzel

Senzel, the Reds’ top prospect, per MLB Pipeline, is an important part of Cincinnati’s future, but it’s uncertain when he’ll debut and what position he’ll play. The 23-year-old is a third baseman by trade, but with Eugenio Suarez signed to a long-term deal, Senzel has been learning center field. Even with second baseman Scooter Gennett sidelined eight to 12 weeks with a groin strain, the Reds opted not to move Senzel back to the infield to play a position where he has experience. He will continue to play center field at Triple-A Louisville. More >

NL WEST

D-backs: LHP Robbie Ray

In 2017, Robbie Ray was one of the best pitchers in the NL. Last year, he struggled to find that consistency. With Patrick Corbin gone, the D-backs need him to be the Ray of 2017, pitching deeper into games and forming a potent top of the rotation with Zack Greinke. More >

Dodgers: SS Corey Seager

Seager was an All-Star shortstop his first two seasons, but what will he be after Tommy John surgery on his right elbow and an arthroscopic labrum repair on his left hip? It’s tough enough returning from either of those operations, never mind both. He hasn’t had a setback in his recovery, but he hasn’t faced the test of playing every day either. More >

Giants: C Buster Posey

Posey has given the Giants no reason to believe that he won't be ready for Opening Day, but questions remain about what kind of workload he'll be able to handle behind the plate as he works his way back from major hip surgery. More >

Padres: OF Wil Myers

When he’s healthy, Myers has proven he’s an All-Star-caliber bat. He hasn’t been very healthy over the past two seasons -- and when he has been, the righty-hitting slugger has fallen into some prolonged slumps. Myers is now solidified as an outfielder, and he finally has got some lineup protection. The Padres think he’s due to bounce back. More >

Rockies: RHP Jon Gray

The last two years, Gray started on Opening Day and was considered the team's No. 1 pitcher. However, even though his numbers would be considered almost decent for past Rockies teams (12-9, 5.12 ERA), Gray endured a brief option to Triple-A Albuquerque, and was left off the roster for the postseason. Even more, struggles in a few high-profile games (2017 NL Wild Card Game, 2018 Opening Day, his final regular-season start) have sparked a narrative that he can't handle the big moment. But Gray believes a greater understanding of executing his pitches is the answer. More >