Has the slider helped or hurt Nunez?

Leo Nunez will be undoubtedly on his way out of the Marlins’ bullpen anytime soon, given that he is the most obviously available player on the team’s roster. One of the reasons teams are showing an obvious interest in Nunez is that he has been successful in picking up saves this season, and I’m sure the Marlins would like to suggest that is the addition of a slider to Nunez’s arsenal. One of the biggest supposed problems in Nunez’s otherwise stellar 2010 season was the he seemed to have dropped the use of his slider in favor of his changeup, and the Marlins took great strides to fix that problem this season. Nunez has upped his slider usage, which should theoretically help his play against right-handers.

But how has Nunez’s addition of a slider changed his performance against righties this season? Just looking at the numbers, it seems difficult to tell.

The numbers look quite interesting. In terms of BABIP, there is an obvious difference that could have something to do with his pitch selection. By FIP, it appears that he has improved, but his strikeout rate is well down from last season against righties (though he did also drop his walk rate). Part of that is simple regression, and you can see in the difference in his overall strikeout decrease (26.3 percent last season versus 22.7 percent this season) that he was probably due for a slight drop from his peak strikeout rate last season. Just from a superficial look, there seems to be a lot of moving parts in the switch to more sliders and fewer changeups, and perhaps a quick look at some Pitch f/x data may help elucidate what is going on.

Usage Patterns

First off, let us make sure that Nunez has actually changed most of his usage pattern from last year to this year.

Indeed there has been an increase in slider usage, but it has not been entirely at the expense of Nunez’s changeup, which may very well be his best pitch. He has cut into his changeup and fastball usage equally in order to re-accomodate the use of his slider.

Performance

But how has the slider performed? Let’s take a look at some typical numbers for Nunez’s slider in 2010 and 2011 against righties.

Compare these numbers to those seen by his changeups in those same time periods.

These samples are not large, a byproduct of Nunez being a reliever and analysis of only his right-handed hitter plate appearances. Still, one thing that we can see when comparing the two pitches is that they actually look similar at best. Over the last two years, they have had exactly the same whiff rate (calculated as whiffs per swing taken). Hitters are swinging more often at the changeup, which is a good thing for the changeup given that the two pitches have equal whiff rates, leading to more strikes with the changeup. Over the last two years, hitters have actually hit Nunez less hard on the changeup, with a slugging percentage on contact (SLGCON) of .454 versus a .533 mark against the slider. Then again, there have only been 15 sliders that have been put into play and one of those was the home run against Aaron Rowand that convinced Nunez to stop the slider alltogether.

The point of taking a look at those two results was to see if there was significant split in terms of effectiveness of the two pitches since Nunez has increased his effectiveness last season. It does not seem like there is a major difference in terms of how well the two pitches are fooling hitters, but the Marlins likely expected that the changeup was getting hit harder or better by hitters. It seems like that has not been significantly the case, and it should not be terribly surprising to anyone. Yes, the changeup from a right-handed pitcher is typically a less efficient pitch against righty hitters, but Nunez’s changeup seems to stellar compared to the average change. Even against right-handers, it still has forced 57.5 percent of balls in play to go on the ground, which could lead to singles but are much less likely to go for multiple bases. The slider is less likely to get balls on the ground and its increased use, combined with the decreased fastball use, is likely the reasoning behind the drastic fall in ground ball rate for Nunez against righties.

But what about that BABIP? Some of it was undoubtedly due to bad luck. Nunez gave up 10 hits in 21 balls in play on his changeup in 2010, and some of those undoubtedly were squibblers that got by the porous Marlins infield (seven of the ten hits were singles). In a small sample of 21 balls in play, a lot of randomness can happen, and I think the Marlins may have overreacted. As you can see, hitters are not doing all that well on balls in play against the changeup this season.

Prognosis

Is there a chance that the slider is adding to the changeup’s effectiveness? I think so, but that would be difficult to determine with the data we have obviously. One thing I do think that the Marlins can do is encourage Nunez to once again use the changeup more often against righties while at the same time maintaining his usage of the slider in a way to “make hitters respect” the pitch. If Nunez’s slider is decent (his overall results say it isn’t over his career), then limiting its use while still keeping it around should be more beneficial than having him split the slider and changeup almost evenly. If anything, it may induce more ground balls and keep Nunez safer from the home run, a problem that has plagued him and Marlins fans in the past. If he does not get a chance to do that here, then he may be able to in his eventual new team, but it should be something the pitching staff considers. Again, I don’t advocate removing the slider entirely again, but an increase in usage of Nunez’s awesome changeup is probably advisable.