Justin Bieber laced up his cleats, popped off his shirt, and got really pumped up while playing soccer with his bros.

The Biebs hit up UCLA's campus Tuesday afternoon for a pickup game on one of the soccer fields, and at one point was standing at full attention calling out a play.

We're told several college students gathered around the field to watch JB in action and get a peek at his new torso tattoo ... and he put on quite a show.