Walter McCarty’s education as a coach came from a very unpopular voice here in Boston. But without it the former Celtics reserve forward might not be answering questions as a new assistant for Brad Stevens. McCarty — who was hired by Stevens to fill out the Celtics coaching staff with Ron Adams and Micah Shrewsberry along with holdovers Jamie Young and Jay Larranaga — spent three seasons starting in 2007 as an assistant coach at the University of Louisville under his former C’s coach Rick Pitino. It was there where he learned the intricacies of what a coach does behind the scenes and how to find a voice as an assistant from a guy who has brought three different programs to the Final Four. “Working for Rick Pitino taught me a lot. It really prepared me for how to prepare for opponents how to scout games how to teach and develop players and how to speak and communicate with players as well” McCarty said from the Celtics practice facilities before a private basketball clinic with MarShon Brooks for YMCA of Greater Boston youth yesterday. “I think without those three years and that schooling that education under Rick Pitino I think this would have been a tough get.” It was McCarty’s first crack at coaching and the transition back into the college game after a lifetime in the NBA could have been a challenge. But one of his former co-workers didn’t see it that way. “He was kind of known as an NBA guy and I wasn’t sure how he would be able to transition into college and he was phenomenal” said Richard Pitino son of Rick and a former assistant at Louisville with McCarty for two years. “The thing that was amazing to me was his lack of ego.” Assistant coaches in college do more of the grunt work on the road on the recruiting trail which is where McCarty said he first met Stevens but a major part of that job description is being a soundboard for the players. The big question for McCarty is how he is going to connect with point guard Rajon Rondo. McCarty said that he doesn’t have a long relationship with Rondo even though they both hail from the University of Kentucky and that he doesn’t think that aspect was one of the main reasons why Stevens hired him. Richard Pitino who is entering his first season as the head coach at the University of Minnesota saw McCarty handle Cardinals upperclassmen and Big East stars Earl Clark and Terrence Williams with ease mostly because of his long pro career. “He’s going to deliver the right message” Richard Pitino said. “(Brad Stevens) will be able to trust in him to do that. He will be a great liaison from the players to coach Stevens. . . . He was the type of guy if we needed him to talk to one of the players he would get that message across the right way.”