Here is 1 X-factor player in each division race

As the dog days of summer continue and the 2025 season enters the stretch run, there’s much to be decided for how the playoff field will materialize.

While we have a good idea of who will be playing in October -- the FanGraphs playoff odds have 11 teams with at least an 80 percent chance of making the postseason -- it’s less clear which teams will be winning their respective divisions. Entering Wednesday’s games, the NL West (Dodgers and Padres) and AL West (Astros and Mariners) have two teams tied at the top of the division, while two other division leaders (Phillies and Blue Jays) have a lead of five games or fewer.

With more than 40 games remaining on the schedule for each team, there’s ample time for things to change in the coming months. The question is: which players have the best chances of impacting the divisional races?

Here are the huge X-factor players who could determine the divisional races, going in order from the smallest to the biggest division leads.

AL West: DH Yordan Alvarez, Astros

There’s no shortage of X-factors in an AL West division that has has the Astros and Mariners locked in a tie for first place with a 67-53 record, this after Seattle reeled off wins in nine of 10 games. But it feels like Alvarez can be the single biggest player who could impact this race. It’s been a lost season for the slugging Alvarez, who posted a .646 OPS in 29 games before going on the injured list with a right-hand fracture on May 5 and subsequently dealt with numerous setbacks.

Alvarez is reportedly heading in the right direction and could progress to take live batting practice this weekend, but there’s still no timetable for his return. With Isaac Paredes potentially out of the remainder of the regular season with a hamstring strain, there’s a serious lack of thump in the Astros lineup right now. If Alvarez -- who owns a career .959 OPS in 658 games -- returns soon, he can help ensure that Houston hangs onto the division, not to mention help the Astros make a deep playoff run.

NL West: LHP Blake Snell, Dodgers

The Dodgers rotation is finally starting to get healthy just in time for the stretch run in the playoffs. With Snell, Tyler Glasnow, Shohei Ohtani (the pitcher) and Emmet Sheehan back in the fold, the Dodgers can feel a bit better about their chances to win the NL West. With that said, the Dodgers will need more than just their healthy pitchers returning -- Los Angeles needs some players to step up as the club has gone 15-20 since the beginning of July.

Of all the potential X-factors on the Dodgers, Snell feels especially important considering he was signed as a frontline starter who could pitch in Game 1 or 2 of a playoff series. After missing four months with left shoulder inflammation, Snell returned earlier this month and his presence -- and which pitcher the Dodgers get -- will loom large down the stretch.

If Snell pitches like the Cy Young pitcher we saw in 2023 or for most of 2024 -- or like he did in his most recent start when he struck out 10 Blue Jays hitters in five scoreless innings -- that could catapult the Dodgers to winning the division and perhaps returning to the World Series.

AL East: RHP Shane Bieber, Blue Jays

The Blue Jays have a 4 1/2-game lead over the Red Sox with roughly an 80 percent chance to win the division, according to the FanGraphs playoff odds. With the Yankees spiraling out of the race, Boston appears to be the top team that could dethrone Toronto at the top of the division.

To help stave off a surging Red Sox team, the Blue Jays could find a serious reinforcement in Bieber. The longtime Cleveland starter was traded to the Blue Jays at the Deadline and hasn’t thrown an MLB pitch since April 2024 after undergoing Tommy John surgery. When healthy, Bieber is unquestionably one of the better starters in baseball. Bieber -- who is likely to make one more rehab start before returning to the Majors -- will likely give the Blue Jays a half-dozen starts to gauge how well he returns.

If it’s anything close to the 2019-23 version, the Blue Jays could very well wrap up the division in short order in September. Perhaps more importantly for Toronto, Bieber could be the club’s Game 1 starter in the playoffs.

NL East: DH Mark Vientos, Mets

The Mets and Phillies had been playing leapfrog for first place in the NL East for much of the season, but New York's recent skid has allowed Philadelphia to take a five-game lead in the division. Perhaps more importantly for the Mets, they have slid down to the third Wild Card spot and only hold a two-game lead over the Reds. The Mets would love to catch up to the Phillies, but their biggest task at this juncture might be simply making the playoffs.

In terms of New York's X-factor, Vientos certainly fits the bill, as he’s experienced a steep decline after a breakout 2024 season. After slugging 27 home runs with an .837 OPS last season, Vientos has only homered seven times this season while posting a measly .641 OPS. Vientos is making more contact and hitting the ball just as hard but he’s struggled to get those batted balls in the air, leading to a 6.0 percent drop in barrel rate, the second-largest drop among qualifying hitters.

The 25-year-old’s problems don’t seem so pronounced that he couldn’t quickly turn it back on again. If he starts slugging like he did for most of last season, that could be a pivotal development to help the Mets win the division.

AL Central: OF Riley Greene, Tigers

For most of the season, the AL Central’s X-factor would have likely felt like the least important of any division, given that the Tigers led the division by as much as 14 games on July 8. Much has changed since that time, however. The Tigers are 16-20 since July 1, while the Guardians have gone 22-14, shrinking Detroit's division lead to 5 1/2 games and opening the door for Cleveland to make a run at the division.

There are plenty of reasons for Detroit’s skid, but Riley Greene’s struggles have been one of the biggest problems. After posting an .887 OPS with 19 home runs in 83 games through the end of June, Greene has a .681 OPS and 53 strikeouts in 34 games since July 1. The home runs (8) have been there, but Greene has been whiffing far too much, while running a .237 on-base percentage.

In all likelihood, Greene and the Tigers will be fine and hold onto the division. More importantly for Detroit, getting the roster right in time for October is going to be the most important storyline the rest of the way.

NL Central: RHP Cade Horton, Cubs

In one of the more surprising developments of the Trade Deadline, the Cubs were surprisingly quiet, only bringing in utility man Willi Castro and pitchers Mike Soroka, Andrew Kittredge and Taylor Rogers. Whether or not the Cubs’ relative inactivity hurts their divisional chances remains to be seen, but the direction puts a lot of faith in their current group of starters, notably Horton.

Horton, the No. 7 overall pick in the 2022 Draft and MLB Pipeline’s No. 52 prospect entering the season, has been a boon to the Cubs rotation, posting a 3.18 ERA in 79 1/3 innings. From a run prevention standpoint, he’s been even better since the All-Star break, as the soon-to-be 24-year-old hasn’t allowed a run in four starts (22 2/3 innings). The big question: how sustainable is this?

According to ERA estimators like expected ERA (4.27) and FIP (3.90), Horton has been a tad lucky to get to this point. That makes sense considering he has a 21st percentile strikeout rate (18.0 percent) and has allowed a lot of hard contact (8th percentile barrel rate). If Horton -- who pitches on Wednesday night against the Blue Jays -- keeps up his elite run prevention, perhaps Chicago could erase their 7 1/2-game deficit behind the Brewers in the NL Central. If he can’t, it might be a tall task for the Cubs to get there.