Red Sox pitcher Richard Fitts was having the best outing of his career on Saturday, until the injury bug bit the Boston righty in the bottom of the sixth inning against the Chicago White Sox.

TAMPA — An MRI revealed Red Sox starter Richard Fitts has a mild right pectoral strain. He left his start Saturday against the White Sox in Chicago after five dominant innings. He had imaging done Monday.

The Red Sox have placed rookie right-hander Richard Fitts on the 15-day IL, and to fill his spot on the roster they’ve called up a former Rookie of the Year winner.