AP PHOTO - Pittsburgh Pirates starting pitcher Mitch Keller throws to a Chicago Cubs batter during the first inning of a baseball game in Chicago, Saturday, Aug. 1, 2020.

CHICAGO — Pittsburgh Pirates right-hander Mitch Keller exited his start against the Chicago Cubs on Saturday night because of discomfort on his left side.

Keller, one of Pittsburgh’s top young pitchers, was visited by a trainer after he bounced a curveball to Willson Contreras with two out in the third inning. After a short conversation, he walked off the mound and was replaced by Chris Stratton.

The 24-year-old Keller surrendered long solo homers by Ian Happ and Javier Báez earlier in the inning.

Keller was selected by the Pirates in the second round of the 2014 amateur draft out of Cedar Rapids Xavier and made his big league debut last May. He pitched five effective innings in a 5-1 victory at St. Louis in his first start this season.