College basketball superstar Grayson Allen just got his captain's chair back from Duke ... and celebrated by droppin' a 1-handed HAMMER on a teammate in practice.

May have been a little too much sauce from Grayson ... who got all up in Jack White's grill for the posterization. His other teammates seemed to dig it, though.

Hard to blame Allen for being a little extra springy ... he finally regained his team captain title after being in Coach K's doghouse all junior year, and is primed to have a HUGE senior season.

Still ... might wanna save that action for UNC.