About five and a half weeks ago, Yu Darvish threw one particularly exceptional pitch -- exceptional even when stacked against the rest of his body of work, to the extent that hyperbole almost didn't do it proper justice -- against the Yankees, and Jason wrote about it over at BP thusly:
I was confused until the seventh inning, when catcher Mike Napoli appeared to be using a different sign for the pitch than the standard fastball, placing an L between his legs when he wanted the pitch with the extreme arm-side run. The announcers referred to the offering as a two-seamer, but as I stated, the movement was way more extreme, as was evident by the catcher’s pre-pitch setup and anticipation of the pitch (he expected run). The best example can be seen in the sixth and final pitch of Darvish’s seventh-inning matchup against Raul Ibanez, as the standard fastball morphs into a reverse slider that runs away from the hitter like the hitter has cooties.
I wanted to assume that it was just a four-seamer that had late arm-side explosion, because Darvish’s four-seamer has serious movement, but this pitch freaked out and ran away like nothing I have ever seen before. ... Not that Darvish needed another pitch to put in his already crowded bag, but the extreme running fastball was an aspect of his game that I either failed to recognize and appreciate early on or had been unsuccessfully executed up to this point. I was fully aware that his fastball had plus-plus movement, but I’ve never seen a fastball with legs like that. From a scouting perspective, that’s easy 80-grade movement, regardless of what you call it.
Here, for the record, is what said pitch looked like in action (I didn't make this .gif, but I don't know the creator, so I can't throw a hat tip at anyone here):
In any event ... with the count sitting at 2-0 on Howie Kendrick in the bottom of the sixth inning, Darvish unleashed another unique heater that seemed to defy the accepted conventions of baseball physics. The pitch was released at 92 mph, or two miles per hour slower than the pitch against the Yankees, but the late arm-side explosion was even more evident with this offering, as the baseball deviated from its plane and darted in hard on Kendrick's hands during the final 15-20 feet of its journey to the mitt:
Here, for the sake of comparison, is the Gameday view of the pitch:
I've watched every pitch of every Darvish start thus far this season, and these are the only two pitches out of a sample of 1,172 pitches that I can recall exhibiting such an extreme degree of arm-side run. They're also among the nastiest tailing fastballs that I've ever seen in my life, period. The sabermetric concensus after the first such pitch against the Yankees was that this was more of a freak occurrence than anything else -- the perfect storm of finger placement, grip tightness, arm action, release point, luck, and atmospheric conditions conducive to generating so much late break. This, I think, safely qualifies as the second such pitch thrown by Darvish in a major league uniform.
In a discussion on Tom Tango's site regarding another such freak pitch (Daniel Bard's 99 mph two-seamer last year), one commenter referred to it as a possible "four-sigma event" -- that is, an event that's at least four standard deviations away from the mean, or farther away from the mean than 99.9 percent of all events in a normal distribution. I like that terminology. I'm going to call those two Darvish pitches "four-sigma pitches," and I'm going to do it without worrying much about the risk of exaggeration.