"We needed a fresh arm in the event that we needed to go multiple innings," Red Sox manager John Farrell said.
Ross tossed 2 1/3 scoreless innings in Friday's loss to the Angels, his first appearance since giving up three runs without recording an out on May 8. The seldom-used reliever pitched to a 5.14 ERA in 14 games this season.
Ross having Minor League options remaining factored into the decision.
"No other specific reason for sending him down," general manager Ben Cherington said. "I would like to see him get consistent work. We still think he could be a weapon in our bullpen at some point, and so hopefully he'll get that for a little while at Pawtucket."
Alec Shirkey is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.