Bello will start next Wednesday against the Mariners, Chris Cotillo of MassLive.com reports.
There are a few moving parts to Boston's starting rotation, but manager Alex Cora has opted for a six-man rotation through the end of next week. James Paxton is entering the rotation Friday and by the time the Red Sox reach San Diego next weekend, Garrett Whitlock (elbow) could be ready to roll. Following the series against the Padres, Cora is expected to finalize a decision on a five-man rotation, which could include Bello starting in the minors. The Red Sox do not want to stall his development by putting him in the bullpen.