Where did Kelvin Herrera’s Strikeouts Go?


Mandatory Credit: John Rieger-USA TODAY Sports

Following an outstanding 2014 season, Kelvin Herrera has gotten some deserved recognition. He’s been a great pitcher for a few years now (basically his entire major league career outside of a fluky month in 2013), but a 1.41 ERA will open up a lot of eyeballs. He’s set to enter arbitration this year, and there has been some consideration of a contract extension.

Some fans expressed concern over giving guaranteed money to a setup man like Herrera, partially because he’s a reliever and relievers explode at unexpected times, and partially because they are concerned about his drop in strikeouts last season. In his first two big league seasons, Herrera struck out 9.5 batters per 9 innings. Last year, he struck out 7.6 batters per 9 innings.

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It’s totally normal to worry about a decline like that, because striking out batters is usually a good measure of reliever effectiveness. However, I’m not all that concerned with the decrease. There aren’t any other indicators that support such a low strikeout rate, and there’s a more logical explanation for fewer strikeouts than “he’s not as good as he used to be.”

First of all, Herrera’s swinging strike rate was 12.3% last year. That’s lower than it was in 2013 (14.1%), but higher than it was in 2012 (11.1%), when he struck out 8.2 batters per 9. His whiff rate was in line with those of Huston Street, Tom Wilhelmsen, and Zach Duke, who all struck out at least 8 per 9, with Duke racking up more than 11 per 9. Herrera missed bats, but he didn’t get the strikeouts.

There is normally a strong correlation between swinging strike rate and strikeout rate, so when there is a disconnect, it’s worth exploring. In this case, it appears Herrera wasn’t able to get the whiffs when he needed them most, in two-strike counts.

Between 2012 and 2013, Herrera got ahead 0-2 on batters 137 times, and he came away with 64 strikeouts, which is a rate of 46.7%. He also didn’t walk a single one of those 137 batters, which is a walk rate of 0%. That means that if you try to calculate his strikeout-to-walk ratio in those situations, you would see that it’s “CANNOT DIVIDE BY ZERO,” or “ERROR.” Herrera broke math.

In 2014, Herrera got ahead 0-2 on 64 batters, and he came away with 18 strikeouts, which is a strikeout rate of 28.1%. To make matters worse, his walk rate skyrocketed all the way up to 1.6%. Ok, so he only walked 1 batter after getting ahead 0-2, so let’s just focus on the strikeouts.

We know that Herrera’s pitches were still extremely good last year. His fastball still averaged more than 99 MPH, and it had roughly the same amount of movement as it did in the previous two seasons. He also added velocity to his changeup, without sacrificing movement, making it even more effective.

The changeup got slightly fewer whiffs, but his whiff rate still topped 20%. The whiff rates for his fastball and sinker both increased to 13.5% and 11%, respectively, which makes the drop in strikeouts even more strange. His stuff was still there, so why did the strikeouts disappear?

The answer appears to lie in Herrera’s pitch usage. In the two seasons prior to 2014, in two-strike counts, Herrera threw his fastball about 53% of the time. In 2014, in two-strike counts, Herrera threw his fastball about 52% of the time. That doesn’t tell us anything, but stick with me.

His money pitch is the changeup, and he threw it 37% of the time in two-strike counts between 2012 and 2013. Last year, that rate fell to 26%. Instead of throwing more changeups, Herrera threw more sinkers and curveballs in two-strike counts. Neither of those pitches get as many whiffs as his changeup, which helps explain the drop in strikeouts. He wasn’t throwing his best pitch as frequently, and as a result, Herrera allowed more balls in play.

While Herrera does have a knack for generating a lot of weak contact, his sinker and curve don’t really accomplish that any more than his changeup does. A sinker will get a few more grounders, but a changeup also results in a ton of grounders, along with more whiffs. It’s a better two-strike pitch, and especially so when it’s such an elite pitch, as Herrera’s is.

When a pitcher changes his pitch usage that much, it’s usually the result of a conscious decision. It may have been something Herrera wanted to do, or it could have come from a suggestion from Dave Eiland. Regardless of where the idea came from, Herrera’s best bet to collect more strikeouts next season is to get back to relying on his changeup in two-strike counts.

This isn’t to say he can’t be effective in 2015 unless he alters his pitch mix, but allowing more contact in two-strike counts isn’t a good thing. Missing bats with two strikes results in outs basically 100% of the time. The Royals have a tremendous defense, but even the best defenses allow hits to sneak through every so often. Strikeouts make sure nothing is left to chance, and Herrera has the stuff to rack up strikeouts at a very high rate. We’ve seen him do it before, and it shouldn’t surprise anyone if he does it again.