O'Grady's setback further complicates the Marlins' rotation, which entered Monday with the sixth-highest ERA in the Major Leagues. Edinson Volquez underwent Tommy John surgery last week and Wei-Yin Chen is still working back from a left elbow injury he suffered in May. If O'Grady is sidelined, Miami's rotation will likely be Dan Straily, Jose Urena, Adam Conley and Vance Worley.
The Marlins might have to rely even more on their bullpen, which entered Monday with the fourth-most innings pitched in the Major Leagues.
After throwing his 15th pitch -- ball three to Ryan Zimmerman -- O'Grady bent down and placed his hands on his knees before grabbing the right side of his stomach. Mattingly and a team trainer visited the mound but allowed O'Grady to stay in after he threw two practice pitches.
O'Grady thought the ache was just a cramp, but three pitches later -- after forcing Daniel Murphy to pop out -- O'Grady winced and again placed his hands on his knees before limping around the mound. Mattingly and the trainer returned to the field, this time to remove the 27-year-old five batters into his outing. Justin Bour suffered a similar injury July 25 and hasn't resumed baseball activity.
Odrisamer Despaigne replaced the rookie, allowing one run over 3 2/3 innings and collecting his first career RBI on a single in the fifth inning.
"I had a bunch of college buddies here; a bunch of people who still live in the area," said O'Grady, who attended George Mason University in nearby Fairfax, Va. "I had a lot of people out here to come watch, so it's disappointing. I feel like I let them down, let the team down not going deep into the game again. Again, you don't want to mess with an injury. Hopefully it's nothing big."
O'Grady, who has a 5.47 ERA in his first six Major League starts, said he felt fine in the first inning, retiring the side on 12 pitches, including two strikeouts. But the pain emerged during the first at-bat of the second inning, against Zimmerman.
Kyle Melnick is a reporter for MLB.com based in Washington. This story was not subject to the approval of Major League Baseball or its clubs.