Pitcher SwStk% Surgers

Yes, it’s still quite early, but I simply cannot help myself from analyzing my favorite advanced pitcher metric — the swinging strike percentage, or SwStk%. The majority of starting pitchers have only started three or four games, but a metric like SwStk% stabilizes relatively quickly, so the typical small sample size caveats don’t necessarily apply to the full degree. The following five pitchers have enjoyed the largest surge in SwStk% as compared to last year. Let’s see if they are doing anything differently, or if it just seems to be a good run.

Ryan Dempster is second among all Major League starters in SwStk%. Over a small sample, this isn’t so surprising though. With the exception of 2003 and 2011, his SwStk% has sat above 10.0 his entire career, which is quite impressive. The only real change in his pitch mix is that he is throwing his splitter about seven percentage points more frequently. Sure enough, that pitch has generated the highest whiff rate this season, and looking at the pitch historically, it always has. So using the pitch more often would seemingly lead to an increased strikeout rate. So far, it looks as if this is exactly the explanation. Of course, since the pitch usually dives down and out of the strike zone, it may increase a pitcher’s walk rate. What do you know — Dempster’s walk rate is up, while his Zone% is way down. If he continues to utilize the splitter at the rate he has, he may very well set a new career high in strikeout rate…but also walk four batters per nine.

We talked a lot about Yu Darvish after his first start, but not so much since. Remember how we were gushing about his velocity surge? Well, that has disappeared. His velocity is now pretty much in line with how he was throwing last season. The difference so far has been that he is throwing his fastball less frequently in favor of his slider. Obviously, a slider is going to generate more swings and misses than a fastball, but it’s thrown for a strike less often. The whiff rate on Darvish’s slider ranks second among his many pitches. Of course, a slider is usually more difficult to control than the fastballBut like Dempster above, if he continues with this shift in pitch mix, his strikeout rate may remain above last year’s, but his walk rate is in danger of rising as well.

36-year-olds aren’t supposed to post career best strikeout rates. But that is exactly what A.J. Burnett is doing so far in this young season. The odd thing is that he’s doing it by using an identical pitch mix to last season. He has increased the usage of his curveball in recent seasons as his fastball velocity has declined, but that has been a gradual shift. Compared to last year, the whiff rates on both his fastball and curve are slightly higher. Without any obvious explanation here when we dig deeper, the likeliest is that he’s just had a good streak and you should expect a strikeout rate closer to last year over the rest of the season.

Clearly, Tim Hudson is drinking the same old veteran water that Burnett is enjoying. The weird thing about Hudson’s SwStk% surge is that it hasn’t yet corresponded to an increased strikeout rate. This year, Hudson has thrown his fastball less frequently in favor of both his splitter and curveball. Those two pitches rank first and third, respectively, in whiff rate. If he continues with this new pitch mix, he might be capable of reaching a 7.0 K/9 for the first time since 2000. Of course, his walk rate may also remain up, while his ground ball rate stays down.

Adam Wainwright has a 28/0 K/BB ratio. That’s not a typo. He has yet to issue a free pass in 29.0 innings. Unfortunately, just like what happened with Darvish, Wainwright’s increased fastball velocity at the beginning of the season was a mirage. That said, he is throwing his cutter much more frequently this season, and surprise, surprise, it has the highest whiff rate of all his pitches. He may be able to maintain a strikeout rate in the high 8.0 range now if he continues to throw the cutter with the same frequency.