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Potential Starting Pitcher Strikeout Rate Decliners

Yesterday, I unveiled the xK% regression equation 2.0 and used it to discuss pitchers who may enjoy a strikeout rate surge in the near future. Today I am looking into the opposite group — those whose xK% suggest a decline in strikeout rate may be imminent. Similar to the surgers, I am only going to list those pitchers with actual K% marks of at least 20%. If he’s only posting a 15% mark to begin with, but should really be at 10%, do we really care?

Name K% xK% Diff
Tyler Chatwood 22.5% 14.0% 8.5%
Yu Darvish 27.1% 21.0% 6.1%
Johnny Cueto 30.7% 25.4% 5.3%
Masahiro Tanaka 33.7% 28.8% 4.9%
Jon Lester 25.7% 21.0% 4.7%
James Paxton 30.2% 25.9% 4.3%
Adam Wainwright 28.1% 24.0% 4.1%
Max Scherzer 33.0% 29.0% 4.0%

This list is filled with good pitchers off to great starts and it’s fairly obvious that the majority weren’t going to maintain their inflated strikeout percentages even without this equation telling us this.

Tyler Chatwood is intriguing in that he’s an extreme ground ball pitcher and flashes plus velocity with his fastball. Unfortunately, he throws the fastball far too often to induce lots of swings and misses and his primary secondary pitch, the slider, was barely above average in terms of SwStk% last year. Of course, calling Coors Field home also limits his upside. His xK% is almost identical to where he sat the last two seasons, so this is the same Chatwood we’ve seen.

Wow. Since I merged data from both here and Baseball-Reference using the VLOOKUP function, I literally had to go back and check Yu Darvish‘s B-R.com page to ensure I didn’t make a mistake. Turns out, there were no data problems and his S/Str percentage is actually down significantly. Both his cutter and slider have induced fewer swings and misses, plus he’s suddenly turned into an extreme fly ball pitcher. His velocity is fine and he’s throwing more strikes than ever before, so his problems missing bats and killing worms is curious. Given his sub-1.00 ERA and WHIP, you could obviously sell him for as high as can be if you so desire.

Obviously, no one expects Johnny Cueto to maintain a 30%+ K%. But, even his xK% would easily be a new career high. His fastball velocity has jumped over his past two seasons and he’s getting significantly more called strikes than he ever has in the past. That’s what’s primarily driving the xK% surge, so one wonders how sustainable the increase is given his history. Combined with his strong ground ball rate and excellent control, he’s not necessarily a sell-high candidate. Though the injury history is something to consider.

Masahiro Tanaka is currently fourth among all starting pitchers in S/Str rate. Yeah, that splitter is pretty good. I’m still wondering how he managed such pedestrian recent strikeout rates in Japan with such an excellent swing and miss offering.

It’s too bad that James Paxton suffered a lat injury that sent him to the DL as he was showing everyone exactly why I like him so very much. He only made two starts, but if he qualified, he would rank sixth in S/Str rate among all starters. Combine that with an extreme ground ball tendency and passable control, and you have the recipe for a major breakout. Get well soon!