Red Sox manager Terry Francona indicated that Schilling's right shoulder was the cause for concern. The big right-hander underwent an MRI from Red Sox medical director Tom Gill. The Red Sox did not have a definitive update on Schilling as of late Tuesday night.
Schilling will stay in Boston until at least Friday, when he'll be re-examined. In the meantime, he'll work with rehab coordinator Scott Waugh.
Francona said it's too early to rule Schilling out for Sunday's start in San Diego, and he added that the club would update the right-hander's condition on Wednesday.
"I think his shoulder was a little -- he was just having trouble getting loose," Francona said. "With all the humidity [Monday] night, I think our thought would be that it would be easy to get loose. He didn't complain of pain or anything; it's just the ball wasn't coming out [well]."
Schilling was belted around by the Braves to the tune of 10 hits and six runs over 4 1/3 innings.
Since losing a no-hitter with two outs in the ninth inning in Oakland on June 7, Schilling is 0-2 with a 10.61 ERA. In those two starts, he's given up 19 hits over 9 1/3 innings.
"Since Tom and all those guys are familiar with [his medical records], we sent him back to Boston, let him get looked at and just feel better," Francona said. "It seems like we wouldn't be doing our due diligence. It just seems like it makes sense to do that."
The dead giveaway during Monday's start was the radar-gun reading. Schilling topped out at 90 mph. Most of his fastballs were in the mid-80s, uncharacteristically low for Schilling.
Francona, who is now in his eighth season of managing Schilling, has never seen the righty have such a flat fastball.
"That was a tough night," Francona said. "I was kind of squirming the whole game. He got the lineout double play ... but it was an uncomfortable feeling for me."
Schilling has not missed time due to an arm injury since the beginning of the 2000 season, when he was recovering from offseason surgery on his shoulder.
In 1995, Schilling had his labrum repaired and a bone spur removed from his shoulder.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.