A USFL wide receiver was hit so hard on the field during a game on Sunday, his tooth shattered inside of his mouth -- forcing him to grossly spit it out on the sidelines.
The dentist's worst nightmare went down in the third quarter of the Pittsburgh Maulers' game against the Philadelphia Stars in Alabama ... when Isiah Hennie caught a pass and turned up the sidelines looking for a big play.
After about 10 yards, though, Stars defensive back Cody Brown drilled him in the jaw with his helmet -- sending the Maulers wideout crashing to the ground.