Sounds like it happened on a foul ball.
"The Tigers moved McGonigle to the injured list with a right hamate fracture on Aug. 12. He was replaced on defense in Saturday's High-A West Michigan game after striking out in the first inning. McGonigle fouled off a 1-2 pitch in the at-bat, then asked for time and was seen clutching and shaking his right hand before looking uncomfortable swinging at strike three."
Tigers injuries and roster moves (mlb.com)