Utley has a sprained thumb and Polanco has been bothered by an elbow injury.
Utley suffered the injury while sliding into second base Monday night in a failed attempt to stretch a leadoff single into a double against Cincinnati. An MRI on Tuesday wasn't clear about the severity of the sprain. Utley headed back to Philadelphia to see a hand specialist and get more tests on Wednesday.
Polanco has a bone spur in his left elbow. It was hit by a pitch in April and has bothered him since despite two injections to help the healing. He aggravated it while diving last Friday and missed the last three games. He went back to Philadelphia to get more tests on Wednesday.
Polanco is second in the NL with a .318 batting average. He also leads NL third basemen in fielding percentage.
Both Phillies were candidates for starting spots in the upcoming All-Star Game in Anaheim, Calif. Polanco, who trails only Atlanta's Martin Prado in the NL in batting, held a slight lead over the Mets' David Wright in the most recent balloting at third base.
Utley, who's hitting .277 with 11 homers and 37 RBIs, is the leading vote-getter at second base in the National League. He's been the NL's starting second baseman every year since 2006.
The defending NL champions called up infielder Brian Bocock and utility player Greg Dobbs from Triple-A Lehigh Valley. Bocock is batting .179 with one homer. Dobbs was outrighted to Lehigh on June 23 and played in four games, going 2-for-17.
"When you lose Utley and Poly, that's a big part of our lineup," Phillies manager Charlie Manuel said. "At the same time, that's when you give somebody else a chance."
Philadelphia is finishing June with seven players on the disabled list, including two key infielders. If Utley and Polanco are out for more than two weeks, the Phillies would be looking to trade.
"I think we're always looking to get better," assistant general manager Scott Proefrock said. "Now our focus may be a little different than it was."
Senior writer Jerry Crasnick covers baseball for ESPN.com. Information from The Associated Press was used in this report.