Thornton (heel) struck out two batters and allowed one hit over a scoreless inning of relief in Sunday's 8-7 loss to the Pirates.
Thornton was forced out of his prior appearance in Monday's 8-6 extra-inning loss to Detroit when he was struck on the left foot by a comebacker, with the reliever later getting diagnosed with a heel contusion. He was able to avoid a stint on the injured list, and after a few days of rest and recovery, Thornton stepped in to pitch a scoreless eighth inning in the Cubs' final game in Pittsburgh. Thornton has ascended into a key late-inning role in an injury-plagued Cubs bullpen, but he could fall down the pecking order soon. Daniel Palencia (elbow) is close to beginning a rehab assignment and could be back from the injured list before the middle of August, and Chicago could also add another high-leverage piece or two to its bullpen ahead of next Monday's trade deadline.