BOSTON — Jayson Tatum’s return from his Achilles tear was one of the most inspiring stories in sports this year. What Tatum was able to do less than 10 months after his surgery was unprecedented, and will serve as a blueprint for how NBA players recover from this injury in the future.  But once again, Tatum had to watch his teammates from the bench, this time as they lost to the Philadelphia 76ers. “It was tough. I was, I mean, I was upset. I was sad,” Tatum said at his exit interview Saturday afternoon. “I didn’t think it was going to end that way. I spent too much time on the bench watching the team play so I knew how that felt. It just kind of never really crossed my mind, that once I came back everything was going so well. So to have to sit yesterday in the biggest game of the season and just not being able to be out there and be a part of that, obviously because everybody knows how much I care about this game and love being out there. So just having to sit there in that moment, it was just tough.…