# The foul ball, part two: What does it tell us about a pitcher?

April 21, 2008 7 Comments

Last week, I took a look at what a foul ball tells us about a batter. In general, we saw that what type of foul balls a batter hit (whether they were two-strike spoilers or they were basically really long strikes) may have provided a bit of a diagnostic to his mindset at the plate, whether he was a high risk/reward swinger or a low risk/reward swinger. Now, we look at it from the pitcher’s perspective.

Again, I’ve calculated a few basic foul ball metrics, including foul balls per plate appearance, zero and one strike fouls per PA, two strike foul balls per PA, overall contact and swing percentages, and percentage of balls with which the batter made contact that went foul (foul contact). And I ran a big correlation matrix to look at whether any of these metrics were correlated with a pitcher’s batter ball profile, the usual slash stats, and some basic outcome rates.

Batters were fairly consistent from year to year on these foul ball metrics. What about pitchers? Again, I looked at the years 2004-2007 with a minimum of 250 BF. Foul balls per PA (intraclass correlation = .696), contact percentage (ICC = .805), and foul contact (ICC = .753) were all pretty stable. So, there is some repeatable skill in inducing (or not inducing foul balls or getting the ball to go foul when it has been hit).

Splitting the foul balls by when they happened in the count didn’t make for very reliable stats though. (Two strike fouls ICC = .585, 0-and-1 strike fouls = .454). Those numbers are nice, but to be considered reliable, they should be north of .70. Further, there was a moderate correlation (r = .359) between those two stats. Sounds like pitchers don’t control when the foul ball happens, but they do have an overall skill in getting the ball to go foul.

Taking a quick look at simple foul balls per PA gives us some interesting information. A pitcher who gives up a lot of foul balls is more likely to give up fly balls (r = .411) and less likely to give up ground balls (r = -.440). He’s also more likely to strike batters out (r = .440), but not and more or less likely to walk batters (r = -.020). So, it pays to have a pitcher who induces a lot of foul balls, although he might pay for it with more home runs coming off of those fly balls.

The real story though is in figuring out what happens to the ball after the batter makes contact. A higher overall contact rate (again, from the pitcher’s perspective) is associated with higher numbers on all three slash stats (AVG/OBP/SLG, those correlations being .610/.381/.494). It’s also weakly associated with fewer walks (r = -.245), but *very* associated with fewer strikeouts (r = -.844!!!) and more singles (r = .519). Now, given that, we would never want a pitcher who pitches “to contact”, right? Maybe we would.

The foul contact index has some rather interesting findings. Here we see that the ratio of foul balls to the number of all balls hit (foul or in play… or over the fence), has a bunch of strong correlations in the other direction. A lot of foul balls here is related to lower numbers on the three slash stats (r = -.535/-.352/-.387), as well as a higher strike out rate (r = .725), and fewer singles (r = -.491) and doubles and triples (r = -.310). Might have something to do with the fact that foul balls are generally counted as strikes, and strikes are… um, good if you’re a pitcher. Foul contact, strangely enough, does correlate moderately with more walks, however (r = .205). Weird. Moral of the story: you can get by as a pitcher who pitches “to contact”, as long as they’re hitting it foul most of the time.

Who were the league leaders in foul contact in 2007? (Top 20, from highest to lowest, min 250 BF): Rafael Betancourt, Russ Springer, Al Reyes, Juan Cruz, Scott Kazmir, Chris Young, J.J. Putz, Rafael Soriano, Jonathon Broxton, Jose Valverde, Kevin Gregg, Joe Nathan, Alan Embree, Brandon Morrow, Frank Francisco, Matt Garza, Mariano Rivera, Bob Howry, Eric Bedard, and Jake Peavy. Mostly relievers, and some guys with some pretty high-test stuff, but a few guys who aren’t considered “closer material” but still have had good seasons with less-than-classically-beautiful stuff. Maybe there’s something to this.

One other issue worth looking at was brought up by StatSpeak alumnus Mike Fast in his comment on part one of this series. Do a lot of two-strike foul balls mean that a pitcher lacks a “strikeout pitch?” Surprisingly, the answer is no. We’ve already seen that two-strike fouls are a rather un-reliable stat from the pitcher’s perspective, so there’s not a lot of repeatable skill in inducing two-strike fouls. Still, do they correlate well with strikeouts? The correlation is -.172, so there’s a weak relationship in which more two strike fouls lead to fewer walks, but .172 isn’t much of anything. It looks like if the pitcher at first doesn’t succeed in striking the batter out on a two strike pitch, he can try try again.

So what have we learned? Foul balls are a good thing for a pitcher! (Primarily because they count as strikes.) If a pitcher has a repetoire of “stuff” that no one can touch, that’s great! It’s hard to hit a home run if you can’t get the bat on the ball. However, if a pitcher doesn’t have world class gas, it’s OK if he has *tricky* stuff. It might be one of those abilities that hide in the data that no one really pays attention to. Consider, a foul ball means that the batter is thinking “hey, I can hit that!” and so he swings. He aims his bat where he thinks the ball is going, but apparently, he’s a little off and he fouls it off. The pitcher has tricked him! Perhaps foul contact is a decent proxy for how tricky a pitcher’s “stuff” really is. If a pitcher can trick a batter over and over, it means that he’s doing something right.

Next week, we’ll finish up our study of the foul ball (who knew they were so interesting!) by looking at what a foul ball tells us about an at-bat.

Foul contact is 1-fair contact? Then I’m lost.

Some tables, or clearer definitions of terms, might help. Of course, maybe it’s just me. Usually is…

Nice job again, Cutter. You don’t quite say it here (I don’t think), but I infer that foul contact rate is negatively associated with fair contact rate. Is that right? And is that the opposite of what we see with batters?

Foul contact is actually 1-fair contact. It correlates with overall contact rate at -.495 on the pitcher side and -.549 (sic) on the batter’s side. So, the people are either hitting or inducing a lot of foul balls aren’t the type that make/allow contact very much to begin with.

Ack, I’m such a moron! Foul contact looks at all balls with which the batter made contact. Either it went fair or it went foul. Foul contact is just the percentage of those balls that went foul. By extension, foul contact + fair contact = 100%.

Overall contact rate looks at all swings and whether the batter made contact (fair or foul) vs. swinging and missing.

Is there a way to differeniate between an outfield foul ball and a dribbler foul towards the dugout? And would that make any difference in the stats?

It’s not possible with Retrosheet data. I bet dollars to donuts that it would make a difference though.

Very nice work, Pizza! The results are interesting.