September is right around the corner, and that means that MLB roster expansion is just days away. Under the current rules, teams can expand their current rosters to 28 players on Sept. 1, with pitchers only allowed to fill 14 of those spots. The limit on pitchers not only has tamped down the endless bullpen swaps that used to plague baseball's final month, but also has made it more likely that teams give their actual top prospects a taste of the big leagues.
Most of the time, September call-ups don't make an impact right away; sometimes they just fade into obscurity altogether. However, there have also been some all-time great September call-ups including Stan Musial, Fernando Valenzuela, Randy Johnson and Ernie Banks. In short, this is an exciting time for those that follow prospects, and predicting who could get the call when rosters expand is both fun and very, very tricky.
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Here are the top MLB prospects who are among the favorites to get called up in September
Most of these September call-up lists are basically wish lists without much regard for a team's actual needs or place in the standings. Generally, pitchers are more likely to be September call-ups given late-season attrition and fatigue, so they'll get priority here, as are teams with actual playoff ambitions who are motivated to bring up their best players over the season's final weeks.
Andrew Painter, RHP, Phillies
It is honestly surprising that Andrew Painter hasn't made it back to the big leagues already given how much the Phillies have talked him up even during his rehab from Tommy John surgery. However, command issues have plagued Painter during his comeback this year, and Philly opted to keep him in the Minor Leagues to sort things out. While Painter has looked very uneven since the middle of July, the season-ending injury to Zack Wheeler combined with trading away Mick Abel at the deadline could force the team's hand.
Spencer Jones, OF, Yankees
In terms of pure physical specimens, you probably won't find many that top Spencer Jones, who has a very rare combination of size, speed and strength. Jones has been on the warpath in the Minors this season, with a .975 OPS which has led to Yankees fans clamoring for him to be called up to help New York's struggling offense for months now. Jones' strikeout issues remain a problem even with some improvement this year, but it does feel like we should finally see him in September.
Payton Tolle, LHP, Red Sox
The Red Sox have a pitching problem, and at some point, they are going to have to meaningfully dip into their Minor League ranks to fix it. Richard Fitts' injury may lead to Kyle Harrison getting the call, but Payton Tolle absolutely needs to be a part of Boston's roster expansion in September. His extension is absurd, which allows his fastball to play way up, and both his slider and changeup have made strides this year. If the Red Sox want to make a late-season playoff push, they need to call Tolle up.
JR Ritchie, RHP, Braves
This is a weird one, because the Braves are very much not in contention for a playoff spot. However, Atlanta's rotation has been absolutely decimated by injuries which are going to bleed into their availability at least at the start of 2026. JR Ritchie could be a favorite for one of those spots next spring, and calling him up now would allow the Braves to see how he handles big-league hitters and give him some real homework heading into the offseason.