After making 38 relief appearances this season, Medlen was put in the starting rotation and has been unbeatable since then.
He has gone 8-0 in his 10 starts with an earned run average of less than 1.00. He has a 9-1 record overall this season.
Medlen was lifted for a pinch-hitter with two out and two on in the eighth inning, denying him a chance for what could have been his third complete game and second shutout of the year.
That move did not work when pinch-hitter Lyle Overbay flew out to center to end the inning.
Craig Kimbrel came on in the ninth and claimed his 38th save despite giving up a single and hitting a batter.
Josh Johnson (8-13) suffered the loss, giving up three runs on five hits in six innings.