The culprit has been identified.
NFL Media's Mike Garafolo reports it was Patriots running back Rex Burkhead who collided with Tom Brady at practice, resulting in the thumb injury that has throw New England in a tizzy over the quarterback's readiness for the AFC Championship Game Sunday against the Jacksonville Jaguars at Gillette Stadium.
"Rex Burkhead was the running back," Garafolo said on "Good Morning Football." "They were colliding as they were doing some sort of handoff in a little drill. I don't know exactly what happened, but it resulted in a cut. There was blood all over the place and it was significant."
Brady’s right thumb bent back badly when he was smashed into by a running back. Somehow, the ball got jammed back into the webbing between his thumb and index finger and it caused a cut. Might have been the laces. There may be stitches. He’s not taking snaps under center. He can take them in shotgun. He’s trying not to aggravate the thumb between now and kickoff so the reps are at a minimum. He can throw. I have no idea how hard, how far or how accurately.
Brady is listed as questionable for the first time for a playoff game, but Garafolo reports that TB12 "should be good to go."
"Receivers [at practice] didn't notice anything different from what I gather," Garafolo said. "We'll see how much of a factor it is if he has to squeeze it into a tight window, but from what I am told he should be good to go."
Burkhead is also listed as questionable with a knee injury. He hasn't played since the victory over the Steelers Dec. 17.