"He had a good bullpen [session Monday] and he didn't experience anything in his arm, but he experienced soreness in that oblique that he hurt last year in the playoffs," Reds manager Dusty Baker said. "So we'll wait and see."
Cueto was forced to exit Game 1 of the National League Division Series at San Francisco after only eight pitches because of a strained right oblique.
On Monday, Cueto threw 45 pitches in the bullpen -- his second mound session since going on the DL -- and used all of his pitches. He threw lightly again on Tuesday, again without issue.
"I always say 'Wait until the next day.' You hope there's nothing, but this time, there was something," Baker said.
Cueto will be examined again on Monday and a potential rehab schedule will be updated then. Rookie Tony Cingrani, who will make his fourth start since replacing Cueto against the Cubs on Saturday, is 2-0 with a 1.50 ERA.
"I'm sure Johnny is as disappointed as anybody," Baker said. "He wants to pitch and help us. Good thing we have the kid and we're pitching well."
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.