ATLANTA — The Atlanta Braves are moving left-hander Jo-Jo Reyes to the bullpen and plan to call up right-hander Kris Medlen to take his place in the rotation.

Manager Bobby Cox said on Friday that Medlen, who is 5-0 with a 0.96 ERA at Triple-A Gwinnett, will be called up to start Tuesday night against Colorado.

"He's throwing great," Cox said of Medlen.

Medlen's strong start moved him ahead of top prospect Tommy Hanson, who is 1-3 with a 1.99 ERA at Gwinnett.

Medlen has allowed only 19 hits while striking out 44 batters in 37 1-3 innings.

He was 7-8 with a 3.52 ERA at Double-A Mississippi last year. He began the 2008 season as a reliever before moving to Mississippi's rotation in June and was 6-5 with a 3.11 ERA in 11 starts.

Reyes is 0-2 with a 6.58 ERA in five starts.

"We'll stick him in the bullpen, see what he can do out there," Cox said. "He gets so close to getting it consistently then for some reason or other it wanders away."

Reyes has allowed only a .133 batting average (4 for 30) against left-handers. He has allowed a .309 batting average to right-handed hitters.

Reyes expects to see mostly left-handed batters as a reliever.

"I think my success so far off lefties is what he's looking at," Reyes said of Cox.

Reyes has made only four relief appearances in seven seasons in the Braves' organization.