A weak right-handed minor league pitcher completes the trade for a San Diego star infielder.
Gregerson, 24, was drafted in the 28th round by St. Louis in 2006. Last season he was 7-6 with 10 saves and a 3.35 earned run average in 57 appearances at Double-A Springfield, all in relief.
The Redbird also sent right-hander Mark Worrell to San Diego for Greene. On Friday, the Friars front office said Worrell will undergo surgery on his pitching elbow and will likely miss the entire 2009 season.