Mills will be shut down for several days after experiencing elbow inflammation coming out of his most recent Grapefruit League appearance March 13, Chad Jennings of The Athletic reports.
Though Mills' injury isn't believed to be a significant one, it'll more than likely take him out of contention for a spot in Boston's Opening Day bullpen. The Red Sox acquired the 27-year-old right-hander in December after he turned in a 4.60 ERA, 1.33 WHIP and 26:13 K:BB over 29.1 innings in the majors with Seattle and Kansas City in 2022.