Rebounding is instinct according to Jared Sullinger. That must be true because Brad Stevens has been watching the Celtics forward’s instinct at work for a long time. “I remember the first time I saw him play and it was in a high school open gym” said Stevens who was a Butler assistant coach at the time. “I called Thad (head coach Matta) on the way home and said I can’t believe how much this kid can do. Not just rebounding but shooting passing. He’s just a very instinctive player. He understands the game. It comes very easy to him. We’ve been better with Sully on the floor. The numbers bear that out in the first three exhibition games. Hopefully that continues.” Considering many of the other numbers from the Celtics that have stained the box score over the three exhibition games leading into last night’s rematch with the Knicks in Verizon Wireless Arena it’s impossible not to notice Sullinger’s progress. He’s the Celtics’ leading scorer (12.8 ppg) and rebounder (6.5 rpg). He was slightly more subdued last night with 12 points and five rebounds during the team’s first win of the preseason under Stevens beating the Knicks 111-81. But for those wondering about the best Celtic during the four games of this preseason it is quite possibly the same guy who said he wasn’t “close” on the first day of training camp. Sullinger by his own admission is overweight and in a never-ending search for better conditioning. He won’t say how much weight he’s lost since the start of training camp because he doesn’t know. He doesn’t look at the scale. “I haven’t checked myself since middle of September” said Sullinger. “I’m just mentally trying to get better and better. I don’t want to have no hiccups. Just keep working hard and get into the best shape possible.