WALTHAM — As Celtics  practice ended Wednesday, Ray Allen  went through the meticulous 3-point and free throw shooting routine that has made him a perennial NBA All-Star and future Hall of Famer. While the rest of the team fled to the locker room, only Allen and one other player were left on the floor — rookie JaJuan Johnson .
‘It’s a huge learning experience,” said the former Big Ten  Player of the Year and First Team All-American of playing catch-up in a shortened training camp. “I learn something new every time I step on the court with these guys.’
Johnson (or, as Kevin Garnett  calls him, “Rook” or “New”) joins a veteran Celtics team, so his role will change from a primary scoring option to complementary role player, and head coach Doc Rivers  feels the rookie is slowly starting to figure out how to implement his game at the NBA level.
‘He’s starting to learn who he is,” said Rivers. “He knows he is a jump shooter, and he is starting to be comfortable enough to take that shot. Today was the first day when he picked and popped, caught it and shot it. The other two days he would catch it and try to make another play.”
Another adjustment the 6-foot-10 power forward needs to address is his slim frame. Johnson was a force in the paint at Purdue. During his senior season, his 20.5 points per game mostly came from his aforementioned mid-range game, but Johnson managed to average 8.6 rebounds and 2.3 blocks. Early on in training camp, however, Rivers says the rookie is getting ‘beat up’ at practice.
“He’ll dunk, because he’s athletic as heck,” said Rivers. “We’re going to run stuff to get him rolling to the basket, and you can throw it up in the air, and he’ll go get it. As far as post presence? Not early, but that’s fine. We don’t need that. We’ll go get that somewhere else.”
Johnson said he spent the offseason working on his core strength, which will pay dividends battling other big men in the paint. ‘It’s a mindset. I’ve dealt with it my whole life. I know people are going to try to be physical with me. I just try to be aggressive back.’
Of course, Johnson’s development was impeded by the NBA lockout. The labor dispute, more than anything, was a lifestyle change for the 22-year-old. ‘It was real tough,” he said. “It was one of the toughest times I’ve had to deal with. I’m used to having to do something, whether it’s going to class or going to practice.’
Fellow Celtics rookie and college teammate E’Twaun Moore signed with a team in Italy temporarily, something Johnson said he would have considered if the lockout continued a few more weeks.
The affable big man is happy to be in Celtics green and will most likely see plenty of action in the preseason opener this Sunday in Toronto.