Facing Barry Zito with one out in the top of the fifth, Votto grounded a soft roller toward third base and was slow getting out of the batter's box. He jogged to first base as he was thrown out by Pablo Sandoval.
Votto didn't believe he was seriously injured. He originally hurt his knee Friday when he went from first to third base on a hit in the fifth inning of Cincinnati's 5-1 win.
"[Friday] night sliding into third base, I jammed it a little bit," Votto said. "Today I tried to play through it and it started acting up."
Votto, who was 0-for-3 in the game, was replaced by Miguel Cairo before the bottom of the fifth. Whether he could play in Sunday's series finale remained unclear.
"We'll have to see. I certainly didn't feel good," Votto said. "I don't see why this should linger. There is nothing structural. It's an instance where last night it happens sliding sometimes. Today with the short turnaround, it lingered a little bit. I will be fine."
Votto deferred his status to manager Dusty Baker and head athletic trainer Paul Lessard.
"He's day to day and we'll re-evaluate it and analyze it in the morning," Baker said. "It depends how sore he is and how he feels."
One of the best hitters in baseball, Votto is batting .350 with 14 home runs and 47 RBIs this season. His 33 doubles and .471 on-base percentage lead the Majors and his 60 walks are tops in the National League.
June was a particularly hot month at the plate for Votto, who batted .392 and finished it with a NL-best 38 hits, 10 doubles and 20 runs. He is a sure bet to start in the All-Star game in Kansas City. During the last balloting update Monday, he led the entire NL in votes.