Well, that part's obvious. But I'm curious about how anyone could tell from a picture who was calling the cadence.
They obviously aren't perfectly synchronized, and Quincy seems to be slightly behind Vinny in the running of the play. Why? We don't know. Maybe they were going on their own cadences, maybe his center didn't snap the ball on time, maybe he bobbled the snap, maybe he was running a different "half-speed" than Vinny, maybe Vinny was going full-speed and Quincy was going half-speed or three-quarter speed. Nobody knows any of that from a picture. And neither do we know that, a split-second after this picture was snapped, Quincy didn't look any different from the way Vinny looks in the picture -- head pointed at the ghost-RB's chest, left foot out, left arm extended, ball higher and turned sideways. He's obviously in the process of sticking out his left arm and picking up and moving his left foot. And I'm guessing they're both going toward the ghost runner.
This is why teams videotape practices instead of having a photographer go around snapping still photos.