Cole Hamels is struggling to miss bats, and it may signal long-term problems for the Rangers

Cole Hamels had a disastrous return from an oblique injury, but his inability to get swinging strikes this season stem from before the Rangers starter was injured.
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Cole Hamels made his first start on Monday night after spending two months on the DL with an oblique injury, and the results were not pretty. He gave up individual runs in the first, third and fourth innings, before being blown up by Cleveland’s offense in the fifth. By time the book closed on him, he had surrendered seven runs on eight hits and four walks in 4 1/3 innings. Despite the Rangers pounding Carlos Carrasco for eight runs in 3 1/3 frames, they lost 15–9. It was hardly a triumphant return for Hamels.

The season-long numbers on Hamels paint an equally ugly picture. The oblique injury has limited him to six starts and 37 innings, but we can’t simply wave away his performance based on small sample size. He owns a 4.38 ERA, 5.31 FIP and 1.32 WHIP. Most troubling, however, is his sudden inability to miss bats. Hamels has fanned 16 batters this season, the same number that he has walked. His 6.7% swinging-strike rate is befitting of a pitcher like Bartolo Colon or Doug Fister, not one who has struck out more than 23% of the batters he has faced across a 12-year career.

Hamels’s velocity is down significantly for each of his pitches this season. That shouldn’t be a huge surprise for a pitcher in his age-33 season approaching 2,400 career innings, including the postseason, and is clearly part of the explanation for his disappearing strikeouts. At the same time, Hamels was never a pitcher who subsisted entirely on velocity. His four-seamer never sat at an average higher than 93.6 mph for a full season, and it was more in the 91–92 mph range when he was in his heyday with the Phillies. Velocity is definitely an issue, but it cannot be the only issue.

If any element of Hamels’s stuff stood out over the years, it was the movement on his pitches, specifically his curveball and changeup. For example, check out this curveball to Mike Morse.

Or this changeup to Bryce Harper.

Both of those pitches started out looking like strikes, but dove out of the zone, getting the batter to commit to swinging at a pitch he couldn’t possibly hit. Inducing swings on pitches out of the zone was a hallmark of Hamels’s game. Fangraphs tracks Pitch F/X plate discipline stats going back to 2007, the second season of Hamels’s career. In every year through 2016, he got hitters to swing at 31.3% or more of pitches he threw outside the strike zone, a metric termed o-swing rate. A rate that high typically places a starter in the top 30 in the league. Indeed, Hamels has never finished worse than 19th among starters in o-swing rate. Over the last four seasons, he ended ninth, ninth, 11th and first.

This season, Hamels can’t buy a swing on a pitch outside the strike zone. His 24% o-swing rate ranks second-worst in the majors, better than only Antonio Senzatela’s 23.1% mark. It’s hard to wrap your head around just how dramatic a fall this is, both from Hamels’s career numbers, and what he did just last season. He has lost 10 full percentage points of his career and 2016 o-swing rates. That’s nearly a 33% drop in one season, something that wouldn’t seem possible if it weren’t unfolding right in front of our eyes.

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Here’s another way to think of just how shocking it is that Hamels suddenly can’t get anyone to swing at his pitches out of the zone: The league-average zone rate—the measure of pitches thrown in the strike zone regardless of whether they’re swung at—has ranged from 47.6% to 50.6%. Let’s split the difference, and call the league-wide zone rate for Hamels’s entire career 49.1%.

To contextualize what Hamels’s precipitous drop in o-swing rate this season actually means, we’re going to make a series of assumptions. They aren’t perfect, of course, but they still serve the purpose of conveying just how damaging Hamels’s inability to induce swings on pitches outside the zone has been this year.

First, we’re going to assume that Hamels more or less mirrors the league-wide zone rate from 2007 through the present day of 49.1%. Second, we’re assuming that Hamels pitches a full season at a typical pitch-per-start workload, a safe assumption given that he made at least 30 starts for nine straight seasons. That streak will come to an end this year, but the illustration is easier to work by accounting for a full season. With those assumptions underlying our experiment, Hamels would throw approximately 1,670 pitches in the zone, and 1,610 pitches outside it over a full year.

Now, we’re working just with the 1,610 pitches outside the zone, which would make up Hamels’s o-swing rate population. The loss of 10 percentage points, down to 24% from 34%, translates to 188 fewer swings on pitches outside the strike zone. Even if we change our calculation to reflect the 23 starts he’s on pace to make, he would lose 118 swings on pitches outside the zone. Given that the majority of those will result in whiffs or weak contact, it’s easy to find the main culprit behind Hamels’s struggles this year. Forget about velocity. Hitters have found a way to lay off Hamels’s “pitcher’s pitches” for the first time in his career.

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This might be an irreversible problem. The best way to measure movement, especially for a breaking ball, is by measuring spin rate. The more revolutions on a pitch, the more it is going to break. Daren Willman, the creator of Baseball Savant and a must-follow on Twitter (@darenw) walked me through creating data sets for cumulative spin rates over a certain time period. The spin rate on Hamels’s curve this season is nearly identical to last year, but down significantly from 2015.

Spin rate is all about the force one can put on a pitch, just like velocity, and we know that generally declines as a pitcher ages. If Hamels is losing velocity as dramatically as he is, chances are he’s also losing spin rate at a similar pace. It may have just taken one more year to manifest itself. If that’s the case, we’re likely looking at a new normal for one of the best pitchers of the last decade.