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
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.