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06/07/09 8:43 PM ET

Upton exits early with left shoulder injury

D-backs outfielder aggravates joint on swing in 10th inning

SAN DIEGO -- D-backs outfielder Justin Upton left Sunday's game after the top of the 10th inning with an aggravated left shoulder.

Upton swung and missed at a 1-1 offering from Padres closer Heath Bell and winced. After being looked at by a trainer and manager A.J. Hinch, Upton stayed in and swung at the next pitch to strikeout.

Upton was then replaced by Gerardo Parra in right in the bottom of the 10th with the score deadlocked at 6.

Losing Upton would be a huge blow to the D-backs. The 21-year-old was recently named the National League Player of the Month for May.

Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.