Valdez was starting at second base in place of Brandon Phillips, who strained his left calf in Tuesday night's game against the Padres.
"He had a stiff neck to start the night and he's been champing at the bit to play more," Reds manager Dusty Baker said. "Valdez slid in at second that made it even worse and I could tell the way he was walking around out there and couldn't turn to his right or left that he was in bad shape."
Valdez, who was replaced by Miguel Cairo, had walked twice before leaving the game.
After Cairo, the Reds have no other second basemen listed on the depth chart.
"Hopefully he'll be better tomorrow," Baker said. "If not, we've got to do something else."
Mark Clements is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.