A Somewhat Unnecessary Examination of K-BB% Splits

Since we’re past the point in the season where most pitchers have faced enough batters of each handedness for us to give some weight to their strikeout and walk rates, my plan was to take a look at pitchers who struggled against hitters of the opposite handedness last year to see if any had made any improvements so far this year. But in that pursuit I got completely sidetracked when I found a couple of guys who surprisingly had a reverse split in K-BB%.

The first name that threw me off was Ubaldo Jimenez. Since 2010, Ubaldo has been, what can only be considered, good against left-handed hitters. His K-BB% against lefties is 13.7% in that time frame compared to the league average which ranged from 9.3% to 11.2% in that span. On the other hand his K-BB% against righties was only 9.3%, which is below average. Prior to 2010 he had the L/R splits you’d expect. From what I can tell, things changed when he began relying on his four-seamer and sinker equally against lefties as opposed to relying much more heavily on his sinker. He’s always been able to generate more whiffs with the four-seamer than the sinker against lefties.

As you can see from the chart on the left, he’s started to rely more on the sinker than the four-seamer again this year and last, but he’s maintained the reverse split by using his splitter more, which is the pitch he generates the most whiffs with against lefties. Of course all of this is borderline meaningless for fantasy owners because Ubaldo’s velocity is down another couple of ticks this year, and he’s been downright terrible. As you can see below from his velocity chart, it’s hard to expect his velocity to bounce back even to the reduced spot it was at the last few years. It should also be noted that Ubaldo’s reverse split sort of tracks with his loss of fastball velocity. He started getting fewer whiffs against righties with his fastball when he lost velocity, which was at the same time his reverse split developed.

The other surprising name that popped up was that of a guy I seemingly can’t escape this year, Ian Kennedy. I drew the Padres rotation when we were doing our depth chart discussions in the preseason. I ended up making Kennedy one of my bold predictions. And I discussed Kennedy a couple of weeks ago when I examined some starters who were living off their fastball early in the season. In none of those pieces did I stumble on to the fact that Kennedy’s K-BB% has been better against left-handers the last four years. The reason seems to be the fact that he’s able to get lefties to swing and miss at his four-seamer at a much higher rate than righties. His changeup is very effective in that regard against both, and his curveball is decent, but it’s the difference in fastball effectiveness that seems to be the big difference.

In the most recent piece I linked to I discussed how Kennedy’s only pitch with a positive pitch value was his four-seamer. A couple of weeks later that still holds true, and the gap between his fastball effectiveness and the effectiveness of his other pitches continues to widen. I noted that I’d like to see his curveball become a plus pitch for him again as it was in 2011, which was his best year. But that seems unlikely to happen at this point. The fastball velocity gains are going to have to stick around for him to have an ERA in the threes for the first time in three years. So far the velocity is holding steady.