The left-hander could be ready to start this weekend in Philadelphia. Manager Walt Weiss decided to give him more time to let the finger fully heal.
"We wanted to wait the last few days to see how that cut healed and make a decision," Weiss said. "We're going to push him back a couple of days."
The Rockies called up left-hander Chris Rusin from Triple-A Albuquerque. Rusin was claimed off waivers from the Cubs last September. He was 3-2 with a 6.29 ERA in six starts and one relief appearance in the minors.
Rusin made 20 starts for the Cubs from 2012-14 and faced the Reds twice during his career, going 0-1.
"We feel like Rusin has a little history with these guys, playing in the same division with the Cubs," Weiss said. "That can work either way."
Colorardo's rotation is in flux because of injuries. Right-hander Jordan Lyles is scheduled to start Friday in Philadelphia, but he's been bothered by a sprained toe on his left foot, injured during his appearance last Saturday.
"Jordan we're still monitoring, too," Weiss said. "We don't feel like it's a DL situation, but he might be in same boat where we have to make an adjustment for one start. But we're not overly concerned about it."
Colorado opened a roster spot by optioning reliever Yohan Flande to Triple-A. He was called up this month and gave up six runs in 7 1/3 innings.
The Reds had lost nine in a row -- their longest slump in 17 years -- heading into the game.