"It's stiff," he said. "I saw a chiropractor today, and he loosened it up. ... It's subsiding a little bit."
Grudzielanek expects to be back in a day or two. Second base was filled by Esteban German on Tuesday and Alberto Callaspo on Wednesday.
"It's hard when you're feeling good at the plate, but it's just something you have to deal with," he said.
On May 18, Grudzielanek was leading the American League with a .331 average. His average has slipped to .290 since then.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.