Watch: Athletics' Alonso leaves game after fouling ball off knee

That hurts just to watch.

Oakland Athletics first baseman Yonder Alonso was forced to leave Wednesday night's game against the Houston Astros in the top of the eighth inning after fouling a pitch from reliever Luke Gregerson directly off his kneecap. The extent of the injury is not yet known.

Alonso is in the midst of his finest season in the majors, hitting .283 with 17 home runs and 38 RBIs in 69 games. At last count, he was third among American League first basemen in All-Star voting, but an injury could put his hopes in jeopardy.

Alonso was replaced by Rajai Davis, who struck out on the next pitch.