The game will be made up as part of a day-night doubleheader on Sunday. The first game starts at 1:35 p.m. and the nightcap at 7:35 p.m.
The Phillies won the opener of the four-game series Thursday night to move within three games of Milwaukee.
Scheduled starters Hamels (12-9) and Manny Parra (10-7) will start Saturday. Milwaukee will send Dave Bush (9-10) and Jeff Suppan (10-8) to the mound Sunday. Joe Blanton (2-0) and Myers (9-11) will pitch for the Phillies.
Myers would be going on three days' rest. He said he wanted the ball Sunday after losing to Florida on Wednesday, but the coaching staff waited to see how his arm responded.
"Myers had a very good day in the bullpen," Phillies manager Charlie Manuel said. "He's ready to pitch."
Hamels wasn't too enthusiastic about moving up a day to pitch on normal four days' rest in the nightcap of a day-night doubleheader against the New York Mets last Sunday. Hamels struggled and the Phillies lost to the Mets, missing an opportunity to move into a tie for first place in the NL East.
Now Hamels has five days between starts.
"He's at 208 (innings pitched), so you have to be careful with him," pitching coach Rich Dubee said.
Not too long ago, it would've seemed improbable that Myers would be counted on to pitch such meaningful games. The Phillies demoted their opening-day starter on July 1 after he went 3-9 with a 5.84 ERA in his first 17 starts.
But Myers has been outstanding since returning. He's 6-2 with a 1.90 ERA in 10 starts.
"Goes to show you things can change quickly," Manuel said.
Both teams are off Monday, so a doubleheader could've been avoided. However, the Brewers voted against playing on their off day.
"It was a hard decision. It was debated, debated and debated," Milwaukee manager Ned Yost said. "We need a break."
Phillies shortstop Jimmy Rollins agreed.
"We'd rather keep our off day," he said.
Manuel and Dubee would've preferred waiting until Monday.
"I don't like doubleheaders," Manuel said. "It's tough to win two games and it's tough for our pitching."