With an added day of rest behind Peacock, Charlie Morton will start Tuesday and Joe Musgrove on Wednesday.
The substitution for Peacock (2-0, 0.87 ERA) follows his 4 1/3 innings of one-hit ball last Monday in a spot start for Dallas Keuchel, who was on the disabled list. Peacock racked up eight strikeouts against the Tigers in Houston's 1-0 win.
"One, it's always nice to give pitchers extra rest," Hinch said. "No. 2, Peacock's pitched well enough to deserve another start. You'll get another look at him against a good team. Pushing Morton back gives him extra rest and Musgrove, after last night's start, is going to stay on regular rest."
Peacock was available out of the bullpen Saturday against the Orioles, Hinch said, but would not enter the game unless there is extra innings or a pressure situation. If Peacock does not enter, he will throw a tuneup bullpen session like a normal starter does before a scheduled start.
Thursday, Fiers gave up 10 hits and three earned runs in 4 2/3 innings against the Tigers. He also surrendered a Major League-high 18th home run this season in Houston's 7-6 win.
Fiers (1-2, 5.21 ERA) gives the Astros a right-handed long-relief arm -- similar to Peacock's role -- and was told about the swap Saturday. Fiers will be available out of the bullpen Monday against Minnesota for what could be a temporary alteration to the Astros' five-man rotation, Hinch said.
"We'll put Fiers in the bullpen for the time being for the Minnesota series and see where that takes us," Hinch said. "I don't want to rush to judgment and say that it's a long-term change, but it's really the way things have lined up. As I told Fiers today, it's not necessarily for longer than the Twins series, we'll make the determination as we go, but that's how we're going to go.
"Starters take great pride in their spots and there are only five of them on a team. [Fiers] took it like a professional and understood this is the way we were going to do it. It wasn't a long conversation."
Christian Boutwell is a reporter for MLB.com based in Houston. This story was not subject to the approval of Major League Baseball or its clubs.