ATLANTA -- Kris Medlen is replacing Jair Jurrjens in the Atlanta Braves' rotation and will start Tuesday against the Marlins.

Manager Fredi Gonzalez said Saturday Medlen will move to the rotation unless the team trades for a starting pitcher before Tuesday. Jurrjens was in the bullpen for Saturday night's game against the Phillies.

Medlen was 5-0 with a 3.86 ERA in 14 starts in 2010, when he was 6-2 overall. He missed most of last season following right elbow ligament-replacement surgery. He is 1-1 with one save and a 2.48 ERA in 38 games this season.

"He's been great, he's been really, really good," said Gonzalez of Medlen. "He's been valuable to us. That's why it's a hard decision to take him out of the bullpen."

Atlanta's rotation has been boosted by the addition of Ben Sheets, the former All-Star who improved to 3-0 with Friday night's 6-1 win over the Phillies. Sheets has allowed only one run in three starts.

Gonzalez said general manager Frank Wren is still looking for help, possibly including a pitcher, before Tuesday's trade deadline.

"I can tell you this from the conversations Frank and I have had ... we're looking to upgrade," Gonzalez said, adding those efforts were continuing "up to 20 minutes ago."

The rotation now includes Tim Hudson, Tommy Hanson, Mike Minor, Medlen and Sheets. Brandon Beachy was a top starter before he had Tommy John surgery on his right elbow in June.

Jurrjens who spent almost two months at Triple-A Gwinnett this season, is 3-4 with a 7.04 ERA in 10 starts.

Jurrjens allowed 14 earned runs in his last two starts, including six runs on nine hits in only 2 1/3 innings in a 9-2 loss at Washington on Sunday. Gonzalez said the decision to move Medlen into the rotation came after Jurrjens' last start.

Medlen pitched three scoreless innings at Miami on Wednesday. Gonzalez said that outing was an attempt to begin to prepare Medlen for a starting role. Gonzalez said he doesn't expect Medlen to throw more than 65 to 70 pitches in his first start.

Meanwhile, right-hander Peter Moylan, who is returning from rotator cuff surgery and hasn't pitched in the majors this season, was placed on the 15-day disabled list with Triple-A Gwinnett with right shoulder tendinitis.

Also, rookie shortstop Andrelton Simmons, who has been on the disabled list since July 13 with a broken right little finger, said his cast should come off next week. He said X-rays have shown the fracture is healing.

Gonzalez said outfielder Matt Diaz, on the 15-day disabled list with a right thumb contusion, will have his hand placed in a cast in an attempt to help the healing process.