He had been placed on the list last Wednesday, four days after he was hit on the back of the head by a line drive.
He pitched two scoreless innings in a rehabilitation appearance at Triple-A Gwinnett on Saturday, allowing a hit and a walk while striking out five.
Newcomb was hit in the head on June 15 by a liner hit by the Philadelphia Phillies' J.T. Realmuto that left his bat at 102 mph. The line drive hit the pitcher's head so hard that the ball bounced into the protective netting above the visitors' dugout on the third-base line.
Newcomb is 1-0 with a save and a 2.12 ERA in 20 appearances this season.
The Associated Press contributed to this report.