Keppinger fouled a pitch off his knee in the second inning. He drew a bases-loaded walk, giving the Reds a 2-0 lead, and played defense in the third and fourth innings before departing.
The team said X-rays revealed the injury and Keppinger is scheduled for an MRI exam Wednesday.
Corey Patterson hit for Keppinger in the bottom of the fourth and stayed in the game to play center field. Ryan Freel moved from center to right and Jerry Hairston Jr. switched from right to shortstop.
Keppinger entered leading Cincinnati with a .320 batting average and tied for third in the National League with a .406 average with runners in scoring position. He took over as the starting shortstop when Alex Gonzalez opened the season on the disabled list with a broken left knee.