FanPost

Subtracting Out Rick Porcello's Slider

Warning: These numbers need to be taken with a grain of salt. Much like batted ball data, two different sources can classify a pitch as two different pitches if the movement of the two pitches are similar (like a curveball and a slider). However, I thought this would be interesting enough to see what Rick Porcello’s 2012 season would look like without his slider since Pitch f/x gives us enough information where we can subtract out the numbers.

As has been reported, Rick Porcello has scrapped his slider and is throwing his curveball more often. The results during Spring Training have been great. In 24 innings, Porcello has a 3.00 ERA, 0.75 WHIP, 21 strikeouts and zero walks. Has the change in pitches really made him this good? Maybe.

Pitch f/x gives pitching values for each pitch type a pitcher has. Average is 0, positive results are above-average and negative results are below average. Here are the numbers for Porcello in 2012:

4-Seam Fastball -4.1 Runs
2-Seam Fastball 1.8 Runs
Slider -17.3 Runs
Curveball 0.6 Runs
Changeup 0.3 Runs

How bad was his slider? According to Pitch f/x, Porcello’s 2012 slider was the worst rated slider by 7.7 runs (Clayton Richard’s slider was rated at -9.6 runs). We can even go deeper in the stats to see individual batting lines for each pitch:

PA BB K HR AVG OBP SLG
2-Seam Fastball 396 26 44 8 0.310 0.360 0.426
4-Seam Fastball 155 6 28 3 0.292 0.329 0.438
Slider 111 2 17 2 0.394 0.405 0.615
Changeup 103 7 14 3 0.240 0.291 0.406
Curveball 16 0 4 0 0.250 0.250 0.313
Total With Slider 781 41 107 16 0.309 0.349 0.451
Total Without Slider 670 39 90 14 0.294 0.340 0.423
Difference 111 2 17 2 0.015 0.009 0.029

Hitters hit .394/.405/.615 off of Porcello’s slider last year with a total batting line against of .309/.349/.451. By subtracting out the slider, the batting average falls 15 points, the on-base percentage falls 9 points and the slugging percentage falls 29 points. His strikeout rate remains virtually unchanged, which kind of surprises me (13.7% with the slider, 13.4% without).

Giving a quick calculation of innings pitched, (H-AB+GIDP)/3, here are estimated innings pitched per pitch type as well as their FIP:

IP FIP
2-Seam Fastball 89 2/3 4.24
4-Seam Fastball 36 1/3 3.37
Slider 22 2/3 3.01
Changeup 24 1/3 4.41
Curveball 4 1/3 1.25
Total With Slider *176 1/3 3.91
Total Without Slider 153 2/3 4.04
Difference 22 2/3 -0.13

*The innings pitched doesn’t total his real innings pitched. I think this is because of errors (8) and caught stealing (5). (8-5)/3 = 1 inning, exactly how much that I’m off by. I don’t think this is a problem, since we can assume that these events would still happen regardless of the type of pitch he threw.

It’s interesting that his slider didn’t result in a high FIP. FIP probably isn't helpful here, given the small sample size and the fact it only factors in home runs, walks, hit by pitches and strikeouts. Porcello wasn't horrible in those stats with his slider.

Going further down, they even give individual batted ball percentages for each pitch:

LD GB FB
2-Seam Fastball 21.5% 60.4% 18.0%
4-Seam Fastball 19.1% 50.4% 30.4%
Slider 27.5% 46.2% 26.4%
Changeup 18.3% 43.9% 37.8%
Curveball 33.3% 41.7% 25.0%

In order to subtract the slider from this, we’ll need the raw numbers…which they don’t give. We can calculate batted balls by taking AB+SF-K-Bunts. They give at bats, sacrifice flies and strikeouts, but they don’t give bunts. There are 9 bunts that need to be subtracted out, but pitch f/x doesn’t show which pitch type was for each bunt…but MLB Gameday does. According to MLB Gameday, there were 5 bunts on 2-seam fastballs, 3 on 4-seam fastballs and 1 on the slider. Using 2 different sources for this information does make it lack credibility, but at least we can get a good idea. Now we can take the batted balls and multiply it by the percentage to get the raw numbers:

Batted Ball LD GB FB
2-Seam Fastball 316 68 191 57
4-Seam Fastball 115 22 58 35
Slider 91 25 42 24
Changeup 82 15 36 31
Curveball 12 4 5 3
Total With Slider 616 134 332 150
Total Without Slider 525 109 290 126

And then divide it back out without the slider stats:

Batted Ball LD GB FB BABIP
With Slider 616 21.8% 53.9% 24.4% 0.343
Without Slider 525 20.8% 55.2% 24.0% 0.324
Difference 91 1.0% -1.3% 0.4% 0.019

It’s a small difference, but there’s a full percentage point difference of line drive to ground balls in the positive direction. And his BABIP falls almost 20 points. Sure, defense was a big reason why his BABIP was high, but so was his ineffective slider.

Of course, he isn’t just eliminating his slider. He’s replacing it with more curveballs. If it’s an above average curveball, the changes will be even more prominent.

This is a FanPost and does not necessarily reflect the views of the <em>Bless You Boys</em> writing staff.