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Aroldis Chapman may be throwing too many strikes

Aroldis Chapman has halved his walk rate this season, which has earned plenty of praise. But, it may have been an overcorrection that has cost Chapman strikeouts and slider effectivity.

MLB: New York Yankees at Cleveland Indians David Richard-USA TODAY Sports

Michael Pineda is a weird pitcher—one who gives up an alarming amount of runs while maintaining clean peripherals. Since the start of 2015, Pineda carries a 4.3% walk rate (fourth lowest in the majors) …and a 4.75 ERA (eighth highest in the majors). The numbers don’t really add up, and Pineda’s constant underperformance never ceases to confuse.

Although the collective baseball world hasn’t come to a concrete conclusion with Pineda, there is a general hypothesis that could answer some of the oddness surrounding his paucity of walks but horrible run prevention skills. Michael Pineda probably throws too many strikes.

So, how does Aroldis Chapman tie in to Pineda’s conundrum? Chapman, like Pineda, might have fallen victim to the too-many-strikes trap. The flamethrower has been lauded for making adjustments this season to pound the zone, but it could be a counterintuitive move.

Going into this season, one would be hard-pressed to spot weaknesses from Chapman. Perhaps his middling ground ball rate would be mentioned, but the most obvious was Chapman’s career 4.21 BB/9. Although the walks haven’t caused him too much trouble, they were the obvious flaw in an otherwise elite relief pitcher.

As a Yankee, Chapman has made that blemish vanish. He has cut his walk rate in half from 2015 to 2016, and the drastic shift doesn’t look to be a fluke. The lower walks are backed up by a sharp increase in Zone%, from 42.3% last season to 57.8% this year. It’s apparent why many are impressed by this improvement, and, don’t get me wrong, this is an improvement. That said, we could be looking at a double edged sword.

First of all, it should be made clear that I’m not attributing Chapman’s current 2.49 ERA (compared to last year’s 1.63 ERA) to the change in strategy. The uptick in runs allowed is much more likely to be noise or bad luck than anything else. However, there are some negative aspects of Chapman’s season that can blamed on the new approach.

Chapman is defined by his ability to rack up strikeouts, so when his strikeout rate dives to its worst mark since his rookie season, people take notice. Sure, most pitchers would kill for a 13.50 K/9, but it’s low by Chapman’s standards. This decrease in strikeouts (from 15.74 K/9 last season) is supported by a 66.1% contact rate against Chapman. Once again, that’s outstanding for most pitchers, but it would be his worst mark since 2011.

In the past, Chapman has lived on the outside of the strike zone, using it to induce boatloads of whiffs. This has led to the higher walk rate, but the massive strikeout numbers as well. His changed approach means more pitches in the zone, and as a result, less whiffs.

A similar line of thinking can be applied to answer why Chapman’s slider has become more hittable. It’s not that the slider itself is easier to drive, but its effectiveness has decreased as a result of location. Chapman used to live low and in (to the right-handed hitter) with the slider, and it was deadly when thrown there. Now, he has shied away from that area, opting to use it more in the strike zone.

This altered plan of attack with the slider has helped to reduce walks, but it has also made the pitch less effective. Prior to this season, batters carried an absurd .085 batting average and .127 slugging percentage against the slider. This season, they’ve hit .231 batting average with a .539 slugging percentage. These aren’t bad numbers, per se, but a bit disappointing compared to past results. Although there’s some luck and small sample size at play here, part of his decrease in slider effectivity has come from location and attempts to limit walks.

Like many things in baseball, Chapman’s new plan is a tradeoff. A lower walk rate is great, but it’s come with a more hittable slider and fewer strikeouts. The southpaw may have made a slight overcorrection, and it wouldn’t hurt to try throwing the slider out of the strike zone more often in the future.