Fab Melo and Jared Sullinger were involved in their first training session with the Celtics Monday. It was just the start of an accelerated program in an attempt to prepare them for significant roles next season, according to president of basketball operations Danny Ainge.

“Everybody knows we lack size on the interior and guarding the rim is one of our weaknesses,” Ainge said during a news conference at the Jackson Mann Educational Complex in Allston. “And big guys usually do take more time to develop than guards. But we’re going to put these guys on a speed course and get them ready to play.”