Ludwick first felt the issue while running the bases in the fifth inning of Wednesday's game in Chicago. He exited that game after the fifth and hasn't played since.
"The groin is a really nagging thing," acting manager Chris Speier said. "We really want to make sure that he's really close to 100 percent."
The Reds entered Saturday with the luxury of an 11-game lead in the National League Central, which allows them to give guys the extra days of rest.
"There's no hurry there," Speier said. "We're in that situation where we can give him those days. It's not make or break that we need his bat in there. I want to make sure that he's 100 percent before he goes back out there."
Ludwick is second on the team with 80 RBIs, and with a Reds club struggling to score runs of late, his bat is certainly missed.
"He's one of our RBI guys," infielder Todd Frazier said. "In those situations, he's come through a lot this year. When you lose a guy like that for a little while, you're going to be hurting. Other guys have to step up."