Campbell was placed on the 7-day injured list at Triple-A Worcester on Tuesday with right elbow inflammation, Chris Cotillo of MassLive.com reports.
It's not clear how long Campbell might be sidelined, but certainly he won't be an option for Boston's bullpen anytime soon. The 26-year-old has been tagged for 13 runs (12 earned) over 6.2 innings with the Red Sox this season but has pitched well at Worcester, holding a 2.20 ERA and 19:5 K:BB across 16.1 frames.