We're two weeks into September now, which means a few September callups have gotten some playing time. Corey Seager was called up by the Dodgers on September 3rd; Seager was one of the top prospects in the minors, if not THE top prospect. Since his debut, he's done nothing but hit. As of Monday night, he had a 225 wRC+ in 42 PA. I'm sure the Dodgers have appreciated his contributions, especially since there haven't been many September callups who have performed like him.
I went to Baseball-Reference's Play Index to get the first-season monthly totals of each player who debuted from 2010-2014. I then isolated those players who played only in September. There were 931 players who debuted during that timeframe, 205 of whom were September callups (22 percent). To "meet" the comparison to Corey Seager, I looked at only those September callups who had at least 40 plate appearances (so no pitchers for this analysis). There are 30 such players. Since my data come from Baseball Reference, I have sOPS+, which compares that player's OPS to the league, so the comparison isn't perfect. OPS+ tracks decently with wRC+ though, so the comparison should be OK enough.
There's a pretty wide range of performance, as one would expect with rookies over a small sample size. According to this measure, Chris Parmelee was the best offensive September callup from 2010-2014. That blissful month remains Parmelee's best performance; he has never reached a 100 wRC+ since 2011, his debut year. With a .390 BABIP, Parmelee smashed his way to a .355/.443/.592 line with a 186 wRC+. He walked a lot, he didn't strike out much, and he hit for power. Despite the smashing, Parmelee's callup was not impactful for the Twins, who were on their way to a 63-99 season.
Jesus Montero is next on the list. Montero's 2011 September callup and subsequent career trajectory is reminiscent of Parmelee's. With a .400 BABIP, Montero hit .328/.406/.590 in that month for a 166 wRC+. The Yankees finished with a 97-65 record and a division crown, though they were part of one of the craziest days in sports when they lost to the Rays while the Red Sox lost to Baltimore, which knocked the Red Sox out and the Rays in. Montero was the catcher for that game and went 0-4 with a strikeout. Montero did play in Game 4 of the ALDS, which the Yankees won 10-1.
Montero's prospect status and September performance set up for an interesting trade between the Mariners and Yankees. Montero was dealt for Michael Pineda. Though Pineda missed a huge amount of time due to injuries, he is currently pitching fairly well for the Yankees. On the other hand, Montero has struggled ever since his blistering September callup.
Josmil Pinto is the next fellow on the list. Pinto debuted for the Twins in 2013 and rode a BABIP-fueled rocket to a 167 wRC+. The Twins were not competitive, though, and Pinto has not played at all at the major-league level in 2015.
As a Cuban international signee rather than a minor league prospect, Rusney Castillo is a little different. His September callup nevertheless resembles others. A 162 wRC+ during a lost Red Sox season had fans dreaming a bit on 2015 in Boston, but Castillo was not able to repeat his performance. Castillo currently sports a 97 wRC+ and equal fWAR despite more than five times the playing time.
I....don't think Rockies fans want to talk about Rafael Ynoa and his 28 wRC+ this year. Ynoa had a powerless .397 BABIP-fueled 121 wRC+ last year.
A few names down the list is Adam Eaton, who is still playing decently today (2.5-fWAR 2015 season). I'm not sure you can say that about any of the other September callups with blue bars. Osvaldo Martinez last made a major league plate appearance in 2011. Brett Pill hasn't played anywhere in the majors or minors since 2013. Tommy Medica has an 81 wRC+ in the Padres AAA organization this year. Alex Liddi is currently in the Royals AA organization, which I didn't even know. (I'm a Royals fan.) Cory Spangenberg has a 92 wRC+ this year, but at least he is playing in the majors. Dalton Pompey is following his 105 wRC+ September cup of coffee last year with a 60 wRC+ this year. Chris Owings has a 61 wRC+ this year.
Interestingly, some of the better current players have red bars. Jarrod Dyson is a platoon player since he can't hit lefties well, but he plays exceptional defense, is a ridiculous weapon on the basepaths, and hits righties pretty well. Brock Holt (!) has been a roughly-average Swiss Army Knife for the Red Sox. Lucas Duda has been given more playing time over the past two years and has not disappointed. Before injuries derailed his 2015, Devin Mesoraco had a big breakout 2014. Maikel Franco has been good in an otherwise lost Phillies season.
So...a predictor for future success is having a bad September callup? That can't be right. Watch out, Corey Seager. Watch out for your .448 BABIP, 19 percent walk rate, 9.5 percent strikeout rate, and .412/.524/.647 line. History is coming for you.
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