Astros: The curious case of Gerrit Cole’s increased home run rate

Houston Astros starter Gerrit Cole has struggled with the long ball this season.

Coming off a top-five Cy Young Award finish in 2018 and entering his final year before free agency, big things are expected of Astros co-ace Gerrit Cole. While he in many ways looks like himself, his ERA sits nearly a run higher than last year’s, largely thanks to an inflated home run total.

Cole has been bit by the long ball 15 times in 14 starts this year, compared to 19 times total in 32 starts last year. He’s had a couple of particularly rough outings so far this year. The rest of his stats don’t look remarkably different from last year’s, so the reason remains a bit of a mystery.

Other Numbers Still Impressive

Cole actually leads the majors in both strikeouts and strikeouts per nine innings among qualified pitchers, averaging nearly 14 per nine. While his hits per nine rate is a tick higher than last year, his walk rate has actually declined, resulting in a lower WHIP than he posted in 2018. So he’s actually allowing slightly fewer baserunners than he did last year.

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His strikeout-to-walk rate sits at a ridiculous 6.5, which would shatter his career best. He’s averaging six innings per start, which is close to the 6.3 he averaged in 2018. Cole is averaging the same number of pitches per start as he did last year, and his quality start percentage has actually gone up.

Along with his walk rate declining, he’s also hitting batters and throwing wild pitches at a considerably lower rate than in 2018. All these signs point to his control actually being better, yet he’s still getting tagged with home runs.

So, What Gives?

Last year, 7.9 percent of the flyballs Cole allowed ended up leaving the yard. This year, that’s spiked to 15.6 percent. What’s interesting is he’s actually allowing fewer flyballs overall, as his groundball-to-flyball ratio is higher than in 2018.

Additionally, the percentage of flyballs Cole allowed that remained in the infield is at nine percent this year, compared to 15 percent in 2018. In other words, a higher percentage of the flyballs he’s allowing are leaving the infield. So even though he’s allowing fewer flyballs overall, the ones he does allow are simply being hit farther than they were last year.

It’s not as though he’s continually falling behind hitters. His first pitch strike percentage of 62.7 is in line with his career average. The percentage of hitters seeing 3-0 counts (2.4 percent) or 0-2 counts (35.5 percent) are nearly identical to 2018’s marks.

Is There An Explanation?

At this point, the stats don’t seem to give a clear reason for the spike in gopher balls. It could be that Cole is just leaving pitches over the heart of the plate a little too often. It could have to do with hitters further paying attention to launch angles. It could be related to the spike in home runs across the league (e.g. “juiced” baseballs or other theories).

Statistical aberrations tend to correct over time. Sometimes they last a short while, sometimes they last a whole season. This one will be worth monitoring, especially given that Cole is set to test free agency this winter. The size of his next contract could depend on it.

***Statistics courtesy of Baseball-Reference***