Uehara was struck on the wrist by a line drive Friday off the bat of Detroit's Ian Kinsler when he reached back with his bare hand to try to field the ball.
Uehara recovered in time to retrieve the ball and throw out Kinsler, but he was in obvious pain.
Initial X-rays were negative, but when the swelling and pain persisted, Uehara was administered a CT scan on Sunday in Detroit, then flew back to Boston later that day to be examined by the Red Sox medical staff.
The CT scan showed a non-displaced distal fracture, the team said. The Red Sox are expecting Uehara to make a full recovery.
Uehara on Friday night faulted himself for the injury.
"Even if something happened, I reached for it, it would have been my responsibility," he said, as if anyone would have thought to blame him.
"I consider my whole body is a glove once I release a ball."
Uehara, 40, is in the first year of a two-year, $18 million contract. He finishes the season with 25 saves and a 2.23 ERA in 43 appearances for the Red Sox, who will be left scrambling for a closer.
In Detroit, manager John Farrell had mentioned setup man Junichi Tazawa and 33-year-old right-hander Jean Machi, acquired from the San Francisco Giants on waivers July 28, as possible short-term replacements for Uehara.
With Uehara heading to the disabled list, the Red Sox will now be able to recall reliever Ryan Cook, obtained in a cash deal from Oakland at the trading deadline.