Middlebrooks was experiencing pain in his right side, so the club is hoping to rule out an oblique or rib injury. He also underwent X-rays and a CT scan following Tuesday night's game.
"Will has got some soreness on the right side of the ribcage," said manager John Farrell. "He just did get an MRI this afternoon. We don't have the results of that back yet. We do know through the imaging and the tests last night there was no fractures of any kind, so that's checked out. He's sore. He's day to day. That's where we are on both guys."
Pedro Ciriaco, who made two errors in relief of Middlebrooks on Tuesday, got the start at third base. The Red Sox are thin at third from an organizational standpoint, so they can ill-afford to lose Middlebrooks for any length of time.
Prior to the game, Farrell was unsure if he'd be able to use Middlebrooks in an emergency situation. Jonny Gomes looked to be Boston's emergency option in the infield or behind the plate if a situation presented itself.
Ross, who suffered a left quad bruise, thinks starting a game could be realistic by this weekend.
"Woke up today and could bend it," said Ross. "Squatting still felt a little tight. I think there's some swelling in there still, but I think the training staff did a good job. We hopped on it to get treatment a lot last night, and I took a machine home to ice with. I think the second day is usually the big test. If it had been worse today, I probably would've been concerned. Definitely night and day from yesterday."
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. Jason Mastrodonato is a reporter for MLB.com. Follow him on Twitter @jmastrodonato. This story was not subject to the approval of Major League Baseball or its clubs.