Gallegos was promoted by the Yankees prior to Thursday's game against Boston.
Gallegos will likely remain on New York's active roster for the rest of the regular season. He last appeared on the mound with the club against the Red Sox on Aug. 12, giving up just one hit in 2.2 innings while striking out four. The right-hander has made 10 appearances with the Yankees this season, posting a 5.79 ERA and 1.43 WHIP in 14 innings out of the bullpen. He figures to serve in low-leverage situations as a reliever moving forward.