Potential BB% Risers Through the Lens of F-Strike%

Although we have done a pretty good job determining what underlying statistics can combine to formulate a strong expected strikeout percentage metric, unfortunately the same cannot be said for a pitcher’s walk percentage. Though one would assume the majority of a pitcher’s control skill would show up in his ability to throw strikes, whether by throwing first pitch strikes or throwing the ball inside the strike zone, that just isn’t the case. But of course that doesn’t mean that this data is useless.

Although we have looked at this before, I figured I would check it out again just as a reminder of what the correlation between F-Strike%/Zone% and BB% is. I used the same data set I have been using recently, which is all starting pitchers who have thrown at least 50 innings from 2003-2012. The R-squared for F-Strike% was 0.4374, while the R-squared for Zone% was a less useful .0794. Though the F-Strike% metric’s R-squared is rather low, it still would likely rank as the biggest factor when projecting a pitcher’s future walk percentage.

Clearly there is more going on that affects a pitcher’s walk percentage than just the ability to throw first pitch strikes. But since we haven’t come up with a strong regression equation yet, the simplest method to determine potential swings in BB% is to just compare a pitcher’s F-Strike% with his BB%. To do this, I just sorted starting pitchers with at least 20 innings pitched by BB% and eyeballed the corresponding F-Strike%. Those with marks well below the pitchers around him with similar BB% are at risk of walking more batters over the rest of the season, assuming all else remains equal.

Also important to note is that the league average BB% among all starting pitchers is 7.4% with a F-Strike% of 60.7%.

Doug Fister has the sixth lowest walk percentage among all starters with at least 20 innings pitched. Yet, his F-Strike% is both below the league average and at a career low. Hmmmm. Fister has always posted very strong walk rates, but he has done it by throwing first pitch strikes more frequently than the average starter. Not this year. A walk rate that matches that F-Strike% is well above Fister’s current BB%, but it’s hard to believe he will suddenly lose control to the point that he posts a BB% worse than league average the rest of the way. Still, it’s something to keep an eye on.

With a much improved walk percentage and solid ERA to boot, it might be tempting to claim that Andrew Cashner has become a pitcher, transforming from his days as a thrower (I hate that cliché). But if you dig deeper, you realize his F-Strike% is the exact same it has always been, so you have to wonder what’s behind the apparent control improvement. If I didn’t own him in nearly all of my leagues after hyping him so much in the pre-season and didn’t have faith that his raw stuff would lead to a higher strikeout rate moving forward, I would likely call him a sell-high candidate. But it’s hard to jump off the Cashner train now.

With Johnny Cueto returning from the DL, Tony Cingrani is now being shifted to the bullpen. He might get another shot in the rotation later in the season though, which means it’s worth noting that his F-Strike% is rather low. His minor league walk percentages also do not suggest control this good, so you have to expect that BB% to rise. In addition, I just cannot imagine a starter who throws his fastball over 80% of the time maintaining a strikeout rate anywhere near what he has posted. At some point the league is going to adjust and then it will be up to Cingrani to start throwing his secondary pitches more often.

Woah, Jered Weaver’s F-Strike% has never dipped below 60% over a full season and his worst mark was 59.4% during his rookie year in 2006. He now sports the third worst F-Strike% among all starters with at least 20 innings pitched! Amazingly, it has barely affected his BB%, as it’s only a smidge above his three previous seasons. In three of his five starts this year, his F-Strike% has been below 48%. This is just unheard of for a pitcher who has always exhibited excellent control. It’s hard to continue counting on a guy who has made a living outperforming his expected ERA metrics each season.

Zack Greinke’s F-Strike% is also at a career low and the first time it has dipped below 59%. His BB% is also up only slightly from previous seasons, so you have to wonder how he could continue limiting the walks while failing to throw first pitch strikes as often. His fastball velocity remains down as well and he has now only exceeded an average of 91.0 mph once all year. Last year, his season average velocity was above 92.0 mph. Like with Weaver (whose velocity is also down), I’m not sure what to make of the two and would be nervous about trying to buy low.