Valverde appears to put the baseball in his glove, prepare something in his mouth, then make a spitting motion -- I feel like I'm breaking down the Zapruder film here -- into it before throwing the pitch.
The result of the 1-2 fastball by the way, was a swinging strike for strike three.
Better watch them quick because you know how the MLBAM is about videos. I'm sure it will be gone soon.
And here's a slow motion version of it.