When Aaron Slegers pitched for the Twins on Aug. 17, starting the second game of a doubleheader against Cleveland, he became the 33rd pitcher this season — and fourth Twin — to make his MLB debut as a starting pitcher this season.
Slegers delivered one of the most important pitching performances of the season that day — giving the Twins 6 1/3 innings of two-run ball, delivering innings and a victory Minnesota desperately needed.
At the time, I was curious how common — or uncommon — it was for a pitcher to excel in his MLB debut. With help from Aaron Gleeman from Baseball Prospectus, I gathered the data on all 33 pitchers to make debuts this season by that point and found that, well, it has not been uncommon at all for first-time starters to do pretty well in 2017.
Counting Slegers, the 33 pitchers to debut as starters delivered, on average, starts that went 5 innings with 2.23 earned runs allowed — for a 4.22 ERA. The MLB ERA for all starting pitchers this season is 4.51, so first-timers actually fared better than the average starter.
I gathered up all that data a few weeks ago … and then Slegers didn’t make a second start for a long time … and then I went on vacation.
But now I’m back, and so is Slegers — who made another very important Wednesday start for a Twins team once again starting to slide. This one, of course, didn’t go nearly as well. He made a couple of mistakes — the big one a three-run homer to Lucas Duda after a pair of two-out walks — and ended up going just four innings while allowing five earned runs.
And, as it turns out, his struggles weren’t all that uncommon, either. I looked up the data on the second start of every other starting pitcher who debuted this season before Slegers. Four of them haven’t had a second start, but of the 28 others who did, their average second start produced an ERA of 5.33 — more than a full run higher than their debuts, and well above the league average.
Maybe it’s too small a sample to be relevant, but maybe other factors are at play. For instance, teams might be more protective of pitchers making their debuts and try to slot them in against inferior opponents and/or remove them from games before teams can adjust to them (though Slegers’ debut vs. Cleveland was no easy task). Also, adrenaline could work in the favor of pitchers making their debuts, as long as they are able to harness it for a little extra velocity instead of losing command.
In the case of a second start, opponents at least have a one-game sample of how a pitcher is trying to get major league hitters out.
In any event, Slegers’ clunker on Wednesday didn’t end up costing the Twins. Even after he contributed to giving three Twins leads right back to the Rays, Minnesota had enough offense to claim a 10-6 victory.
We’ll see if he gets another chance this season. If so, you’re on your own with the research on how pitchers fare in their third games.