Hernandez was injured with Class AA Altoona on Sunday.
The injury came at a bad time for Hernandez, who was hitting .325 in July and .307 since May 28.
The Bucs farm system has been hit hard by injuries: Catcher Tony Sanchez had his jaw fractured by a pitch, outfielder Starling Marte had hand surgery, shortstop Brock Holt had a major leg injury,Jeremy Farrell was also out with a leg injury, pitcher Bryan Morris was shut down for a recent start with elbow fatigue, and several other pitchers missed time to various arm issues.
"It seems like every night I get an update and not a good one and someone else is going to miss some time," Stark lamented. "We are hoping that a couple of those guys are close to coming back - Marte and Farrell in the next couple of weeks."
Some good news, after missing a start, right-hander Bryan Morris came back and pitched brilliantly, allowing two hits and no runs while striking out eight in five innings as the Altoona Curve dropped a 2-0 decision to Erie in 13 innings on Tuesday night.