The Red Sox recalled Bello from Triple-A Worcester on Sunday, Chris Cotillo of MassLive.com reports.
The right-hander was in the mix to be called up for a spot start Saturday, but Boston instead turned to Eduardo Rivera to fill Ranger Suarez's (groin) rotation spot. Bello will still join the big club for the final game before the All-Star break and will be available as a long reliever. Since being optioned to Worcester in early June, the 27-year-old posted a 4.34 ERA, 1.43 WHIP and 22:4 K:BB across 18.2 frames in four starts after scuffling to a 6.34 ERA in 12 outings for the Red Sox.