Houston called up right-hander Jeff Fulchino from Triple-A Round Rock to take his place. Fulchino signed a minor league deal on Feb. 7, after appearing in 12 games for Kansas City last season.
Valverde was hit near his right ankle by Orlando Hudson's grounder during an 8-5 win over Los Angeles last Tuesday. He strained his right calf while chasing the ball after it bounced off his leg, but stayed in the game and got the last two outs.
The calf was so sore that he missed a couple of games. He returned on Sunday and pitched the ninth inning of a 3-2 win over Milwaukee, but the calf bothered him and swelled up again overnight.
The Astros planned to let him sit out the three-game series in Cincinnati and see if it healed, but the injury was no better on Tuesday, prompting them to make the move during an 8-3 victory over the Reds.
"I can't do nothing right now," Valverde said as he walked out of the clubhouse after the game. "They need to bring in somebody who can pitch."
The Astros decided they couldn't leave their bullpen short-handed much longer.
"It's best to get it taken care of, just get it healed," manager Cecil Cooper said. "Hopefully he won't have to spend much time on the disabled list."
Valverde has two saves in four chances this season. He had 44 saves in a career-high 74 appearances last season.