Using Pitch F/X Data to Determine if Mariano Rivera Threw a Spitball

by Jeff Zimmerman on Oct 20, 2009 3:53 PM EDT

As some you may have seen (here and here) there is video from last nights ALCS game of what looks like Mariano Rivera spitting on a ball. I am not going to judge what he was trying to do, instead I will look at the physical aspects of the "spitball" and compare it to the other pitches he threw last night. The main advantage of spitting on a ball is to change the spin and direction of the ball. If there was spit on the ball last night, the ball would act significantly different than other pitches Mariano threw. I went to the ever reliable BrooksBaseball.net and saw that the spitball pitch was labeled as a cutter. Imagine that, Mariano Rivera throwing a cutter. There were nine other pitches last night labeled as cutters. Here is the spin and break information on those nine pitches:

pitch_type	break_angle	break_length	spin_dir	spin_rate	spin angle
FC	-9.3	5.3	166	1135	166
FC	-10.6	5.5	159	1053	159
FC	-16.2	5.5	148	1284	148
FC	-17.7	5.1	154	1411	154
FC	-19.0	5.0	152	1556	152
FC	-19.1	4.2	160	1851	160

FC-spitter	-19.9	4.4	156	1698	156

FC	-24.3	4.8	153	1760	153
FC	-26.7	4.1	153	2070	153
FC	-26.9	4.0	160	2096	160

The suspect pitch was not unusual from the cutters he threw. Even if he was trying to spit on the ball for effect, he got no change in break or spin. People can continue to argue his intent, but for actual effects of the "Spitball" there was no actual advantage gained.

The actual mental aspect gained might be huge as players will be looking for him spitting now. It is not like they need something else to worry about when facing Rivera.

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Comments

logic flaw

I’m not saying that your conclusion is wrong, but your premise — “If there was spit on the ball last night, the ball would act significantly different than other pitches Mariano threw” — is logically flawed. He could, of course, be loading up all of his pitches. I don’t think that’s necessarily the case but merely wanted to point that out.

by pip on Oct 20, 2009 5:12 PM EDT reply actions