"It's one of those things where we were trying to get to the lefty and we don't want it to get to the point where it affects his swing," Mattingly said. "When it got close to that, we thought we better give him a day."
Mattingly said Grandal's shoulder has been sore for the past few days and he was replaced by backup A.J. Ellis.
Grandal has hit .284 with 15 home runs and 44 RBIs. The switch-hitting catcher is a mainstay in the middle of the Dodgers' lineup, providing protection for first baseman Adrian Gonzalez.
Mattingly was noncommittal about Grandal's status heading into the next few days, although the club is set to face a left-hander on Friday and Saturday.
"We'll see," Mattingly said. "If it's something that lingers, at least we're in a good spot for it."
Steve Bourbonis an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.