Sexson partially dislocated shoulder
Sexson also has a partial tear in his left labrum and a bruise at the top of the humerus bone.
Sexson was injured on a check-swing in the eighth inning of Wednesday night's 4-3 loss here to the Chicago Cubs.
He fell to one knee and grabbed his non-throwing shoulder in obvious pain before being led off the field by team physicians.
Diamondbacks doctor Michael Lee initially diagnosed the injury as a strained shoulder but an MRI revealed the partial dislocation and other damage that may need surgery after the season.
Lee said there was no immediate timetable for Sexson's return.
"We will have a much better idea of a possible return date once the initial pain from the injury decreases," Lee said.
Sexson played every inning of every game last season for the Milwaukee Brewers before being traded to Arizona in the offseason in a nine-player deal.
"I have grown accustomed over the years to seeing my name in the lineup every day and being sidelined isn't something I'm used to," Sexson said in a statement. "I will not let this deter me from returning and having a productive season."
Sexson has nine home runs, one behind Barry Bonds for the National League lead. He hit a 503-footer Monday night against the Cubs, the longest home run in Bank One Ballpark's seven-year history.
To take Sexson's spot on the active roster, the Diamondbacks purchased the contract of outfielder Doug DeVore from their Triple-A affiliate in Tucson.
Copyright 2004 by The Associated Press
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