Cardinals general manager Mike Girsch told reporters that Rosenthal will undergo the surgery next week. The team had transferred the right-hander from the 10-day disabled list to the 60-day DL earlier in the day.
Rosenthal had been placed on the 10-day disabled list on Thursday with what was called "right posterior elbow irritation."
He was sent back to St. Louis for testing after allowing a homer to Boston Red Sox shortstop Xander Bogaerts on a 91.4 mph fastball last Wednesday. Rosenthal had not allowed a hit on any fastball slower than 96.3 mph before that game, a 5-4 loss at Fenway Park.
Rosenthal exited that game after issuing a walk.
"Something didn't look right," manager Mike Matheny said at the time. "It just didn't look smooth."
In 50 games this season, Rosenthal is 3-4 with a 3.40 ERA and 11 saves. He converted seven straight saves from July 28 through Aug. 12.
Seung Hwan Oh, Tyler Lyons, and John Brebbia are the candidates to become the Cardinals' closer. St. Louis began Wednesday's action 4 1/2 games out of first place in the National League Central.