Justin Upton threw his helmet in frustration on Saturday night, unintentionally injuring teammate Yonder Alonso in the process. The San Diego Padres were playing the Colorado Rockies.

Upset after getting tagged out in an eighth-inning rundown trying to steal following a one-out double, Upton threw his batting helmet -- intending to hit the floor -- which went sideways up and hit teammate Alonso in the head.

Alonso was checked by Rockies doctors and found to have no concussion symptoms. He will be re-evaluated on Sunday.

"I made a big mistake. I was pretty upset about it. It's childish, man. I've got to do better than that," Upton said.