Barnes had doubled and scored in the top of the sixth. But Barnes said after the game that he tweaked the hamstring in the first inning, when he bobbled David Lough's single to center and was charged with an error.
"It's just a little tight," Barnes said. "It wouldn't loosen up throughout the game."
Barnes said he thinks he'll be ready to go for Sunday's series finale.
Robert Falkoff is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.