Originally written on Fangraphs  |  Last updated 11/18/14

The St. Louis Cardinals have a ferocious offense, capable of putting up runs in bunches against any pitcher in baseball. So, on one hand, the fact that they torched Madison Bumgarner for six runs and chased him from the game in the fourth inning can simply be chalked up to a good opponent. On the other hand, the lousy performance was the continuation of a six week trend, and there are reasons to think that perhaps Bumgarner has worn down over the course of the season.



Split
IP
BA
OBP
SLG
BB%
K%
HR/9
BABIP
FIP
xFIP


Mar/Apr
32
0.225
0.283
0.359
6%
13%
0.84
0.240
4.09
4.30


May
34
0.235
0.271
0.403
4%
21%
1.06
0.275
3.39
3.41


Jun
44.2
0.217
0.259
0.323
5%
26%
0.60
0.280
2.56
2.93


Jul
32
0.217
0.279
0.429
5%
29%
1.69
0.263
4.09
2.80


Aug
39.1
0.208
0.261
0.338
6%
25%
0.92
0.255
3.25
3.42


Sep
26.1
0.299
0.370
0.509
9%
19%
1.03
0.358
4.20
4.16


Oct
8
0.385
0.415
0.667
5%
15%
3.38
0.400
4.06
4.36


For the first four months of the year, Bumgarner mostly posted K/BB ratios of nearly 5/1 and kept his BABIP well below average, which is a pretty lethal combination. In September, though, the strikeout rate went down, the walk rate went up, and his BABIP went over .300, leading to a month of pretty poor results. And, unfortunately for the Giants, October has brought more of the same, only to an even more extreme degree.
By itself, the swing in performance isn’t enough to raise any red flags. We’re dealing with 34 innings and 160 batters faced, so random variation could easily be the cause of the slump. After all, no one’s really concerned about Robinson Cano, and he’s having an even worse October than Bumgarner.
But, in this case, Bumgarner’s results aren’t the only thing that changed since September. Here is Bumgarner’s four-seam fastball velocity by month.


Split
FBv


Mar/Apr
90.3


May
90.7


Jun
90.7


Jul
91.1


Aug
91.5


Sep
89.8


Oct
89.6


During the first four months of the season, Bumgarner had two starts — April 17th and June 23rd — where PITCHF/x recorded his average four-seam below 90 mph. Since September 17th, he’s made five starts, and he’s sat below 90 in every single one. Yesterday, the fastest pitch he threw all day was clocked at 91.3 mph – slower than the average fastball he threw in August. This isn’t just a case where he’s varying his speed more, dragging the average down by taking something off on the low-end. He’s simply shifted his velocity range downward, and the top end has gone from 93-94 to 91-92.
Bumgarner’s never been a flame-thrower, and he doesn’t need to throw 94 in order to get people out, but he does need his slider to have some bite to it. Bumgarner’s slider is thrown more often than just about any secondary pitch from any starting pitcher in baseball, and he relies heavily on his slider against hitters from both sides of the plate. In fact, against right-handers, Brooks Baseball suggests he threw his slider just as often as he threw his fastball. That’s extremely unusual for a left-handed pitcher, as the slider has the largest platoon split of any pitch in baseball.
Bumgarner’s slider actually has some cut-fastball tendencies, as it moves horizontally more than it moves vertically, and it’s only four or five ticks slower than his average fastball. Against right-handers, he has learned how to start it over the plate so it looks like a strike, but it ends up on the inside corner or just off the plate, making it a brutal location for opposing batters to make contact with. To illustrate, here’s a heat map of Bumgarner’s slider versus right-handers this year.

And here’s a GIF of what a good Bumgarner slider against a right-handed batter looks like.

That was taken from a start on August 21st where Bumgarner racked up 10 strikeouts in eight shutout innings. When that pitch is well located, Bumgarner is really tough to hit. That month, Brooks’ data says that he throw 197 sliders to right-handed batters and got 37 swinging strikes. In September and October, he’s thrown 196 sliders to right-handed batters and only racked up 19 swinging strikes. Because now he’s throwing sliders like this.

That was the last pitch Bumgarner threw yesterday. It was a flat 87 MPH slider that hung over the middle of the plate, and Carlos Beltran didn’t miss it. That’s not the pitch that Bumgarner wanted to throw, but it’s the kind of slider he’s been throwing too often over the last six weeks. While no one should think that he’s now a true talent .400 BABIP or 3.38 HR/9 guy, he’s also pitching worse than he has all season, and his velocity decline and ineffectiveness of his slider against right-handers are more worrisome than the results.
Of course, Bumgarner has done this before. He famously struggled with diminished velocity at the start of the 2010 season, only to find his stuff against mid-summer before coming up and dominating as a rookie. His April performance this year wasn’t anything to write home about, especially in terms of strikeout rate, and his fastball sat just over 90 then too. In each case, Bumgarner’s stuff has returned, and he’s gone right back to blowing hitters away.
He may very well do that again in his next start. None of this should cause the Giants to give up hope in their young lefty. The greater body of work suggests that he’s a good pitcher who is just going through a slump. That happens.
But, it’s hard to ignore the fact that the slump has come when his fastball velocity decreased and his slider stopped biting. It’s certainly easier to get hitters out when you’re throwing 92 with movement than when you’re sitting at 90 and hanging pitches over the heart of the plate. Whether this will be a continuing issue for the Giants remains to be seen, but they’re going to need the good Madison Bumgarner back in order to win the World Series. Unfortunately, they haven’t seen the good Madison Bumgarner much in the last month.

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