Thanks largely to the expanded rosters, September is a time for MLB teams to get a look at some of their best prospects. No, rosters don't expand now nearly as much as they used to (only two additional spots instead of 15 in the past), but there's still a good chance we'll see some top prospects debut over the final month of the year.
Contending teams will examine their farm system, hoping to patch a hole on their roster and/or find a spark. Teams out of postseason contention will look at their farm system, hoping to find a prospect or two who can help them compete in 2026 and beyond.
There figure to be several impactful prospects that get the call-up in September. If any of them come close to making the list of the most impactful September call-ups in MLB history, the team that rosters said player(s) will be thrilled. With all of that being said, here's a list of the most impactful September call-ups in league history.
The most impactful September call-ups in MLB history
- Billy Hamilton, Cincinnati Reds, 2013
- Fernando Valenzuela, Los Angeles Dodgers, 1980
- Stan Musial, St. Louis Cardinals, 1941
- David Price, Tampa Bay Rays, 2008
- Evan Carter, Texas Rangers, 2023
- Francisco Rodriguez, Los Angeles Angels, 2002
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Billy Hamilton, Cincinnati Reds, 2013
This one might be controversial, but I can't leave Billy Hamilton off this list. Yes, I understand that Hamilton only had 22 plate appearances when he was first called up in 2013, but if we're talking about impact, it's inarguable that Hamilton made lots of it with the Cincinnati Reds.
Hamilton went 7-for-19 at the plate with two walks, but that isn't why he made this list. The fact that he stole 13 bases in 14 tries and scored nine runs in the thick of a Reds postseason race is why. Hamilton wasn't asked to come up to the plate much, but he made the most of those opportunities, and did nothing but thrive in his primary role as a pinch-runner.
Hamilton helped lead the Reds to the postseason as a Wild Card team. He didn't make an appearance in that postseason, but his September was certainly one to remember.
Fernando Valenzuela, Los Angeles Dodgers, 1980
Despite pitching all season in the minor leagues as a starting pitcher, the Los Angeles Dodgers promoted Fernando Valenzuela in September of 1980 to work out of their bullpen. It's safe to say that went better than they could've hoped.
Valenzuela pitched 17.2 innings in 10 games and allowed a total of two runs, both of which were unearned. He didn't have the best stuff in the world, but hitters still couldn't touch just about anything he threw.
The Dodgers missed the playoffs by 1.0 game that season, raising the question of what the 1980 campaign might've looked like had they used Valenzuela as a starter instead of a multi-inning reliever. Regardless, Fernandomania couldn't have gotten off to much of a better start than it did.
Stan Musial, St. Louis Cardinals, 1941
Stan Musial is responsible for perhaps the most dominant September call-up performance we've ever seen. He played in only 12 games for the St. Louis Cardinals down the stretch of the 1941 MLB season, but he slashed .426/.449/.574 with one home run and seven RBI.
Sure, a 47 at-bat sample size is far from substantial, but Musial couldn't have done much more to create a strong first impression. Musial had a hit in nearly half of his at-bats, and perhaps most impressively, struck out a total of one time in those 47 at-bats. He had five times the amount of extra-base hits in his first taste of MLB action as strikeouts.
The signs were there that Musial would become an instant star, and sure enough, he wound up receiving MVP votes in his first full season and wound up being a Hall of Famer soon after he hung up the spikes for good.
David Price, Tampa Bay Rays, 2008
David Price is another example of a starting pitcher who made an impact mostly as a reliever in his first MLB action. Four of the five appearances Price had in the regular season in 2008 came out of the bullpen, and he allowed just four runs (three earned) in 14 innings of work. Price looked good in the regular season, but he wouldn't have made this list had we not discussed what he was able to do for the Tampa Bay Rays in the postseason.
The southpaw appeared in five games in relief for the Rays in the postseason, allowing two runs (one earned) in 5.2 innings of work with eight strikeouts and a total of two hits. Price was particularly impressive in the ALCS, closing out the powerful Boston Red Sox by finishing off a four-out save. Yes, a rookie was tasked with finishing off a loaded Red Sox team in Game 7 of the ALCS. Oh yeah, he happened to strike out three of the five batters he faced.
Price would later become one of the best starting pitchers in the sport, but the impact he had as a rookie reliever is hard to top.
Evan Carter, Texas Rangers, 2023
Hoping to go on a dream run in 2023, the Texas Rangers promoted top prospect Evan Carter to the majors in early September. He made the impact that the Rangers were looking for and then some. Carter slashed .306/.413/.645 with five home runs and 12 RBI in 23 regular-season games, helping the Rangers make the postseason. What he did in October only enhanced his rookie legacy.
Carter slashed .300/.417/.500 overall with one home run and six RBI in 17 postseason games overall. Most impressively, he had at least one hit in all but two of the games he appeared in, one of which he didn't even start. Carter was consistently solid, and by the time the ALCS and World Series began, Carter was hitting third and fourth in the Rangers' order regularly. He led the team with nine doubles in the postseason and was among the team leaders in several other categories.
Carter hasn't quite lived up to the standards he set as a rookie, but Rangers fans will never forget his contributions, particularly in the postseason. Texas might not have won the 2023 World Series without him.
Francisco Rodriguez, Los Angeles Angels, 2002
Francisco Rodriguez wasn't supposed to get called up in 2002. The Los Angeles Angels gave him a look because of injuries to their bullpen, and they reaped the benefits. Rodriguez made five regular-season appearances, allowing no runs on three hits with two walks in 5.2 innings of work. He struck out an absurd 13 batters in those innings.
As impressive as that regular-season showing was, Rodriguez wouldn't have made this list if it weren't for his postseason heroics. Rodriguez pitched what felt like every day in October and was outstanding, posting a 1.93 ERA in 11 appearances and 18.2 innings of work. He allowed five runs (four earned) on 10 hits and struck out 28 batters overall. He won five games and tacked on three holds.
What really sticks out about K-Rod's postseason was that the Angels went 10-1 in games he pitched in. He operated as the primary setup man in front of Troy Percival and was just about perfect when it came to keeping the Angels tied or ahead in games. Having a dominant closer is important, but Percival wouldn't have gotten the save chances in what turned out to be a run to a World Series title without Rodriguez.