Class A standout Mason Williams' season is over because of a torn left labrum.
Williams, right-handed-hitting outfielder, is considered by many the best prospect in the Yankees' system. GM Brian Cashman said he expects Williams to be ready by next spring training.
"It will hopefully be a speedy recovery and will be 100 percent by spring training," Williams tweeted Friday.
In 98 games at Class A, Williams, who turns 21 this month, hit .298 with 11 homers and 35 RBIs. He had an .820 OPS.
The Yankees have had trouble with injuries in the minor this season. Most notably, top pitching prospect Manny Banuelos has missed most of the year with a sore elbow. He has not pitched since the middle of May. Cashman has said that Banuelos will pitch again this season.
Banuelos, 21, had a 4.50 ERA in six starts at Triple-A.