Ramirez was chasing Angel Pagan's pop fly to shallow left Tuesday night when he lunged for the ball at the last minute and hit the ground hard. The ball dropped for a single and Ramirez tumbled over, grabbing his left shoulder as he writhed in pain.
The three-time All-Star and 2009 NL batting champion stayed down for several minutes. He walked off the field, holding his left arm gingerly to his side, with manager Jack McKeon and a trainer.
Ramirez, the 2006 NL Rookie of the Year, is having a down season. He began the night batting .242 with 10 homers and 45 RBIs.
Ramirez was on the disabled list earlier this season with a lower back strain.
Information from The Associated Press was used in this report.