This is bad news for an organization light on good hitting prospects.

Outfielder Mac Williamson, who hit 25 home runs for Class A San Jose last year, apparently has an injury to his right ulnar-collateral ligament and is being evaluated for a possible Tommy John reconstruction surgery.

Williamson, 23, has been dealing with the injury to his throwing elbow all season. Even though he had been ticketed for promotion to Double-A Richmond, Va., he started the season with San Jose because he could exclusively be a designated hitter there. Pitchers hit in the National League parks in the Eastern League.