Howard was held out of Sunday's practice and will be re-evaluated Monday morning.
He might miss Monday night's NCAA tournament's championship game against Duke.
Galloy says Sunday that the junior apparently took two shots to the head in Saturday's 52-50 victory over Michigan State, first banging his head on the floor after a violent collision with two other players.
Then, after returning to the game, Howard took an elbow to head, left the game again and did not return.
If Howard cannot play Monday night, Butler would be without its No. 3 scorer, its second-leading rebounder and its strongest post player.
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