SEATTLE -- Danny Hultzen, the Mariners top left-handed pitching prospect, underwent shoulder surgery in Pensacola, Fla., on Tuesday to repair a partial tear of his left rotator cuff and clean up the labrum.
No timetable was set on the return of Hultzen, currently ranked No. 23 among all of baseball's prospects by MLB.com. But shoulder surgeries are difficult for pitchers and it would seem unlikely for Hultzen to return by next season.
Hultzen, 23, was Seattle's first-round Draft choice in 2011 out of the University of Virginia and the second overall pick behind right-hander Gerrit Cole of the Pirates.
"This is very unfortunate for Danny and his family, but we have nothing but high hopes for a good recovery and rehab," said Mariners general manager Jack Zduriencik. "Danny is a tireless worker and will do everything he can to get back on the mound to start competing again."
The surgery was performed by Dr. James Andrews, one of the premier orthopedic specialists in the country.
Hultzen made seven Minor League starts during the 2013 season, going 4-1 with a 2.05 ERA in six starts for Triple-A Tacoma and also picking up a win with five innings of one-run ball in an Arizona Rookie League rehab start.
Hultzen made his last appearance on Sept. 1 for Tacoma, throwing two scoreless innings after missing most of the second half of the Triple-A season, then threw a simulated game under the supervision of Mariners staff at Safeco Field in preparation for a stint in instructional ball in Arizona and then the Arizona Fall League.
But the shoulder began hurting again when Hultzen went to Arizona and he underwent surgery after tests revealed damage in the shoulder capsule.
In two Minor League seasons, Hultzen has combined to go 14-8 with a 2.82 ERA in 32 starts.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.