Miller, signed as a free agent in the offseason, was 1-3 with an 8.59 ERA in eight starts and 11 relief appearances. He was an All-Star for the Braves in 2015 but was struggling to come back from Tommy John elbow injury.
Biddle was acquired on waivers from the Mariners last Friday. He has pitched in a combined 26 games for the Braves and the Mariners with a 7.54 ERA. He pitched in 60 games for the Braves last season and was 6-1 with a 3.11 ERA and a 1.27 WHIP.