Kendrick (11-9) allowed seven runs and six hits in 1 1-3 innings in a 10-8 loss to the Florida Marlins last Tuesday. He has allowed 13 runs in only 5 1-3 innings in two starts this month, leaving his overall ERA at 5.44.

"I feel like Kyle mentally needs a break," manager Charlie Manuel said Tuesday. "He's mentally and physically in a down period right now I think. Happ was the one that came into play for me."

Happ has no record and a 3.27 ERA in two starts. He has never faced the Braves. He gave up five hits, including two home runs, and three runs in 3 1-3 innings in last Tuesday's loss to the Marlins.

Happ, who has a 5.71 ERA and no decisions in five games overall, said he understands Wednesday's start will be his most important of the season.

"It's one of those things, where you get butterflies until you get through that first inning, that first hitter," Happ said.

"It's definitely exciting. I'm sure it's not their first choice. I'm sure, with the doubleheader they just need somebody."

The Phillies won both games of Sunday's doubleheader against the Milwaukee Brewers to complete a four-game sweep of the series in Philadelphia. The Phillies began Tuesday tied with the Milwaukee Brewers for the wild-card lead and a half-game behind the New York Mets in the division.

Manuel said he has not decided if Happ will remain in the rotation after Wednesday's game.

"Any time we get down under 20 games (to go) we look at every day as a must-win situation," Manuel said. "We want to have who we think is our best option."

Manuel said his decision was based in part on the fact Braves hitters haven't faced Happ. He said he feared Kendrick was wearing down after making 29 starts and throwing 150 2-3 innings.

"It's a long season," Manuel said. "This season is longer than the minor leagues ever dreamed of being.

"Mentally and physically, I think he's at the point where shutting him down for a while might be good for him."

Manuel said that does not mean Kendrick has been shut down for the season.

"I didn't mean that," Manuel said. "I mean we're kind of staying away from him right now.

"Definitely I haven't given up on Kyle and I'm not disappointed in Kyle or anything like that. It's baseball. This is a big season for him. Like I said, he's never been this far before."