Their initial move was to replace him with a pitcher, giving themselves a backup plan in case Johnny Cueto's blister bothered him during his start Tuesday night against the Arizona Diamondbacks.
Beyond that, the NL Central leaders aren't sure how they'll try to replace one of the league's top hitters for up to a month.
"You're bombarding me with questions that I really don't have answers to right now," manager Dusty Baker said. "So let's take it today and then we'll see what we can do tomorrow. We have things in the works."
Votto's injury gives the Reds more incentive to try to acquire another hitter to help them stay in contention. There's no replacement ready in the minors.
The first baseman is batting .342 and leads the National League in doubles, walks, on-base percentage and extra-base hits.
Votto hurt the knee June 29 while sliding into base, but didn't think it was a significant injury and kept playing. He started at first base in the All-Star game Tuesday. When the knee began bothering him again over the weekend, he had an MRI on Monday evening that found the tear.
He decided to have the surgery now rather than try to keep playing with the injury, which could get worse over time. Baker had a long talk with him about it Monday night.
Baker hurt his left knee during his playing career but chose not to have surgery, which wasn't as advanced then. The knee caused him problems the rest of his career.
"I just expressed some of the things the doctor expressed to him," Baker said. "Mine was a little different issue, where I didn't get mine done. I went through a number of cortisone shots and played my last 10 years when I should have had it done right away."
The Reds put Votto on the 15-day disabled list Tuesday and called up right-hander Todd Redmond from Triple-A Louisville. The Reds got Redmond from Atlanta on Saturday for shortstop Paul Janish in a swap of minor leaguers.
Redmond was with Triple-A Gwinnett playing against Louisville when the trade was completed. He switched clubhouses, finished the series with his new team, then went to Columbus, Ohio, for a series when the Reds called him up.
"It's real exciting, especially with the last couple of days — getting traded, switching dugouts and looking at my team on the other side," Redmond said.
Cueto developed a blister on the index finger of his pitching hand while throwing in the bullpen over the All-Star break. The Reds pushed his start back two days to give it time to heal.
Starter Bronson Arroyo lasted only three innings in a 5-3 loss to Arizona on Monday night, forcing Baker to use his bullpen. With questions about Cueto's blister, the Reds decided to bring up another pitcher for the night.
"I was in the bullpen deep and early yesterday, so we need some innings," Baker said. "We've got a couple of guys who have thrown two of three days or three out of four days."
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