Sunday, August 8, 2010

Rivera's Fastballs

So, Mariano Rivera is pretty good. I thought I'd take a look at some of his PITCHf/x plots from 2007-2009. Before we go on, keep in mind that the pitch database that I have does not necessarily accurately categorize every fastball as cutter, sinker, four-seam fastball, etc. It is a well-known fact that Rivera throws only two pitches, well, three I suppose: the cutter and occasionally a four-seam fastball and a two-seam fastball. In the PITCHf/x database, FA, FC, and FF come up, which are generic fastballs, cutters, and four-seam fastballs respectively. Rivera's pitches between 2007-2009 break down and are categorized as follows:

FA: 897 pitches (28.7%)
FC: 1907 pitches (61.1%)
FF: 320 pitches (10.2%)

So bear in mind that some of his cutters which didn't have movement (intended or unintended) may have been categorized as generic fastballs, while some of them may also be two-seam or four-seam fastballs. Now let's take a look at some of his PITCHf/x plots from 2007-2009, split up by fastball type and batter handedness. Again, this is the catcher's POV, right-handed hitters standing on the left and left-handed hitters standing on the right:

The generic fastballs are all over the strikezone, and since these are likely just uncategorized cutters and four-seamers instead of exclusively two-seamers or four-seamers, there's not much to tell from the location plot there. Rivera's cutters, on the other hand, show Rivera hitting all over the strikezone, but consistently painting the outer edge for right-handed hitters and the inner edge for left-handed hitters, some up in the zone and some down and out of the zone. Since we know that Rivera's cutters and their locations are everything to his success in striking out hitters, these plots bolster Rivera's profile that his pitch locations are accurate. Four-seam fastballs (at least 10.2% of his pitches against RHH) are used to go on the inside of righties, but Rivera rarely throws them against lefties. Without a hexagonal binning plot or a filled contour, we can only see that he throws his four-seamer more frequently against RHH than LHH. Let's take a quick look at his pitch breakdown by opposing hitter handedness:

Against RHH:
FA: 497 pitches (31.8%)
FC: 842 pitches (53.9%)
FF: 222 pitches (14.3%)

Against LHH:
FA: 400 pitches (25.3%)
FC: 1083 pitches (68.5%)
FF: 98 pitches (6.2%)

Looks like even if you look at percentages, Rivera throws four-seamers a higher percent of the time against RHH than against LHH, throwing it at least 14.3% of the time against RHH and at least 6.2% of the time against LHH. Rivera's cutters are effective against both RHH and LHH, as they go away from righties and cave in on lefties in order to jam them. However, the use of a four-seamer to paint the inside edge and go toward righties as an additional weapon (the same way that the cutter works against lefties) makes sense, as such a pitch that comes toward lefties from the outside could be more vulnerable.

All this talk of direction and movement begs for movement plots of those pitches. Here they are:

You can see a problem of sample size here. The cutters definitely show consistent positive horizontal movement (movement to the right, away from righties, towards lefties) and that putting that pitch on the right edge of the strikezone is ideal for both righties and lefties. The few four-seamers there are shows some pitches with lots of negative (left) horizontal movement and some with little positive (right) horizontal movement. All of his fastballs have a rising vertical movement effect, with the cutters consistently 5-7 inches higher than a pitch with no spin-induced movement.

Finally, let's look at Rivera's cutters by called strikes and by swinging strikes:

Again, since my database only contains years 2007-2009, the sample size gets smaller and smaller as we get more and more specific. Still, it looks as though Rivera gets more called strikes than swinging strikes against both RHH and LHH. RH hitters whiff more when the cutter is in the zone, while LH hitters are fooled more into swinging on cutters on the inside out of the zone. For both RHH and LHH, Rivera gets the umpire to call strikes when he has cutters coming toward the strikezone and narrowly missing.

That's it for Mariano Rivera. I'm still figuring out the best ways to use hexagonal binning plots. Figuring out the kinks of filled contour plots is still in the works. Hopefully before long, I can make interesting filled contour plots for pitch location heat maps and even spray chart heat maps to show hitters' balls in play tendencies as well as evaluating team defenses on a whole. After mastering graphical techniques for PITCHf/x data, I would love to start doing pitching and hitting scouting reports much like these. Look out for those in the coming weeks.

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