MILWAUKEE -- All-Star left fielder Ryan Braun was pulled from the Brewers' 6-0 victory over Washington on Saturday night because of tightness in his lower back.
Braun, listed as day to day, said muscles on both sides of his ribcage tightened.
"I couldn't breathe," he said.
He said he has never had this type of injury.
"Hopefully, it's just something that's a little irritated," he said. "Whenever you experience or feel something that you haven't felt before, it's obviously a little bit scary."
Braun struck out in the first inning, spiking his helmet into the ground as Ray Durham was thrown out at second attempting to steal for a double play. He said he felt the tightness on a 2-1 pitch during the at-bat.
"I took kind of an awkward swing," he said. "I think it might be some kind of muscle spasm or something because they both tightened up on me."
Braun stayed in the game until the third inning, when manager Ned Yost sent Gabe Kapler to pinch-hit for him.
"We don't need to have any problem there," Yost said of Braun.
Braun is batting .300 with a team-high 30 home runs and 84 RBIs in 114 games.
He has had one of the best starts to a career in major league history. In 227 games since making his debut on May 25, 2007, Braun is first in the majors with 558 total bases, 133 extra-base hits, second with 64 home runs and tied for second with 181 RBI.
His 64 home runs ties him for sixth with Mark Teixeira for the most home runs after two seasons in big league history. The first five are Joe DiMaggio (75), Ralph Kiner (74), Eddie Mathews (72), Albert Pujols (71) and Frank Robinson (67).