Rainey (side) returned to the mound for Triple-A Rochester on Thursday, walking one batter in a scoreless inning, Jesse Dougherty of The Washington Post reports.
Rainey hadn't pitched because of side pain since being demoted to Rochester in mid-August. While he's now returned to game action, he's likely a ways away from being considered for a big-league roster spot. The right-hander was sent down to work on his command after posting a 7.62 ERA and 31:21 K:BB across 26 major-league innings.