Upset after getting tagged out in an eighth-inning rundown trying to steal following a one-out double, the San Diego Padres outfielder threw his batting helmet -- intending to hit the floor -- which went sideways up and hit teammate Yonder Alonso in the head.
Alonso, who was lifted from the game after going 1-for-3 with a walk, was checked by Rockies doctors and found to have no concussion symptoms. He will be re-evaluated on Sunday.
Said Upton, who was 2-for-5 with an RBI and run scored, about his reaction to the play: "I made a big mistake. I was pretty upset about it. It's childish, man. I've got to do better than that."
Padres interim manager Pat Murphy said the show of anger in the dugout was "unacceptable," adding, "Most of the time, showing that kind of anger is not healthy in my mind at all."
Information from The Associated Press was used in this report.