The xK% Strikeout Rate Decliners List by Mike Podhorzer August 19, 2014 Yesterday, I used my updated xK% formula to identify several pitchers who potentially have some strikeout rate upside. Today I will check on with the pitchers on the other side of the list — those whose xK% marks are most below their actual strikeout rates. These are some of the more interesting names. Name xK% K% Diff Jake Arrieta 23.2% 26.2% -3.0% Johnny Cueto 22.7% 25.5% -2.8% Mike Leake 15.7% 18.4% -2.7% Jon Lester 23.2% 25.3% -2.1% Quietly, Jake Arrieta has been one of baseball’s most surprising breakout pitchers this season. In fact, only two articles during this season have been published about him on these pages, one of which was a piece highlighting his eight worst pitches in his previous outing. He has cut his walk rate to a career low, while also increasing his strikeout rate and inducing the highest rate of grounders of his career. That is certainly a recipe for a breakout season. His rate of swinging strikes is up significantly this year, but he’s still only throwing a league average rate of strikes, while his called strike rate is down and foul strike rate is about average. The whole package shouldn’t result in a strikeout rate quite as high as he has posted. Of course, anyone would figure some regression in his future simply based on his past history of mediocrity, but xK% confirms it, while still agreeing that he’s better than he’s ever been. After two disappointing seasons to open his career, an improved mid-3.00 ERA in 2010 and various injuries, who would have guessed that Johnny Cueto would go on to enjoy four straight seasons with a sub-3.00 ERA?! His strikeout rate has now risen for a third straight year, but he really hasn’t seen a whole lot of changes in his strike type rates since last season, when his xK% was a close 21.7%. Throughout his career, he has slightly underperformed his xK% overall, so he has no history of consistent outperformance like he has been doing with his ERA versus SIERA. Cueto has legitimately become one of the best pitchers in the National League, but he’s just not this good. He’s an early favorite to be overvalued in next year’s drafts/auctions. By stranding a high rate of runners, Mike Leake seemingly lucked his way into a low-3.00 ERA last year. Now, he’s posted similar results, but this time actually backed up by his underlying skills. But, are the skills themselves to be trusted? xK% doesn’t think so. He’s made marginal gains in his overall strike percentage, called and swinging strike rates, but they are far too small to validate a three percentage point increase in strikeout rate. With a ground ball profile and good control, he’s still a solid NL-Only option, but in reality he shouldn’t be any more than a streamer candidate in a 12-team mixed league. I’ve taken a lot of heat for my placement of Jon Lester in my monthly tier rankings update and my explanation has been the same. I’m simply not fully buying into his strikeout rate spike. He’s done this before, of course, back in 2009 and 2010, but he was also throwing his fastball over 93 mph on average at the time. Now he isn’t even averaging 92. And his swinging strike rate remains a far cry from those two peak seasons. If he was still a ground ball pitcher, he’d have some additional room for error, but since he’s allowing the highest rate of fly balls over a full season, his perceived value likely trumps my expectations of his rest of season value.