Every season on Sept. 1, big league rosters expand from 25 to 40 active players, therefore allowing teams to potentially call-up a host of prospects. Not every call-up is a future star, however, as a majority of the promotions involve older, organizational role-players just happy to finally reach the Show.
Over the last 25 years, there have been countless examples of September call-ups who make a dynamic impact in a short period of time. So, as we prepare for a second wave of September call-ups, I thought it would be interesting to look back at some of these spectacular performances, by both pitchers and hitters.
For hitters, I sorted September performances by wRC+ (adjusted overall runs created where anything higher than 100 is considered above average) to eliminate each player’s defensive value. I’m only interested in offensive production.
Similarly, I sorted pitchers by ERA-, which is essentially a version of wRC+ for pitchers. But unlike with hitters, the lower the ERA- the better, as a 100 ERA- represents the league average.
So, here is a look at the top five performances by September call-ups in each major category, hitting and pitching, since the start of the 1987 season.
*All stats used in this article courtesy of Fangraphs.com.