Votto, who has a strain of the distal quadriceps near his knee, missed the weekend series against the Phillies to remain in Cincinnati for treatment after an MRI on Thursday revealed the strain.
After the Reds lost 8-3 Sunday, manager Bryan Price said that "we don't want to DL him and find out in two or three days he's ready to play."
The Reds begin a three-game series Monday in Washington and Price couldn't say whether Votto would make the trip, let alone play.
"As long as we're somewhat comfortable having a four-man bench, we won't have to make a decision [on the DL]," Price said.
Votto, a four-time All-Star and the 2010 National League MVP, missed 48 games in 2012 after he had surgery to repair a torn meniscus in his left knee. He's hitting .257 with six home runs and an .859 OPS in 39 games this season.
On Saturday, Price said the Reds were hoping Votto could avoid the DL.
"We're still optimistic that he may not need to go on the DL,'' he said. "That being said, we'll probably have more clarity on that once we get through this weekend series and see how things have evolved.
"We want Joey back as Joey Votto, not as a shell or a shadow of who he is. We want him to play confidently on that knee and that leg for the rest of the season and the rest of his career moving forward. If that means it takes two or three weeks to get it right, that's OK. But we also don't want to put him on the DL if we feel that it might be a four-to-seven-day turnaround.''
Soto played first base and batted eighth in the order against Cliff Lee in the series finale Sunday. With Votto and Jay Bruce (knee) both out with injuries, Brandon Phillips and Todd Frazier batted in the 3-4 spots in the order against Lee.
Information from the Associated Press was used in this report.