I am really busy today (work and other engagements, namely my little brother’s final home high school hoops game of the year), but JaJuan Johnson needs discussing.

Clearly, his 33 minutes yesterday were exciting and encouraging. He did a lot of great things — his run-out for an alley-oop, when he beat everyone down the court by a country mile; the following defensive play, when he reached out to poke away an entry pass and Chris Wilcox ended up finishing another alley-oop; the few jumpers he drilled; and even a number of nearly-missed offensive rebound opportunities during which Johnson’s athleticism and motor were clearly evident. But Johnson also made some rookie mistakes. Think about when Carlos Boozer drop-stepped and lowered his shoulder, and Johnson couldn’t even come close to standing his ground.  Think about a few times when Johnson missed defensive rotations, or the couple occasions when he visibly got in the way of his own teammate’s offensive move.

“He’s got to keep doing it,” Doc Rivers told CSNNE. “One game doesn’t make a star. One season doesn’t make a star. So you’ve just got to keep doing it and he’s got to do it consistently.  He will, like I keep saying. He’s a great kid and he wants to do it. He’s young and he’s still learning focus and all that. But he’s a good player.”

Johnson’s a good player whose production (he’s scored at least 10 points in all three games he’s played at least 10 minutes) has sparked a debate: Does he deserve to join Doc Rivers’ rotation consistently?

Johnson is currently stuck as the fifth big in a league that generally features only four bigs in every rotation. Wilcox has started to play well, giving Boston four big men who Rivers trusts more than any other: Brandon Bass, Kevin Garnett and Jermaine O’Neal being the three besides Wilcox. Johnson is knocking on the door. His problems are easily evident — he struggles physically against stronger opponents and does not yet have a firm grasp on everything the Celtics are trying to do. But it’s also clear that he can score at the NBA level, and his athleticism could potentially give the slow-paced Celtics another dimension.

That’s the biggest argument for giving Johnson and Wilcox more minutes: the duo possesses fast feet and impressive vertical leaps which make them candidates to run the floor alongside Rajon Rondo. For years, Rondo — designed to operate in the land of the open floor — has been miscast as a slow-it-down point guard, mostly because the other Celtics personnel dictates that the team must grind out games rather than open the throttle. This year especially, Rondo can normally be seen either slowing the pace to let his teammates catch up or running the floor by himself in his version of The One-Man Fast Break.

Wilcox and Johnson, not to mention Mickael Pietrus and Avery Bradley, provide athletic options that could unleash Open-Floor Rondo in ways he hasn’t been accustomed to, yet in ways he was built to operate. Think about the two successive alley-oops Rondo threw yesterday — give Rondo a little space and he becomes an artist. Flank him with weapons and he becomes a magician.

Are Johnson and Wilcox’s athletic traits and impressive energy enough to supplant Jermaine O’Neal in the rotation? The minutes allotted to Bass and Garnett aren’t being spread anywhere else when those two are healthy, so Johnson and Wilcox are effectively fighting for O’Neal’s minutes. The battle essentially becomes this: does O’Neal’s defensive presence and veteran sense of calm win out, or can Wilcox and Johnson steal playing time with their exuberance and athleticism — and, in Johnson’s case, a natural scoring sense?

Rivers normally sides with veterans in situations like this. But Johnson is making a case to join the rotation, and if he does, Rondo might have a willing and capable front court running partner.

P.S. — Johnson still doesn’t know all the plays. This matters, but all my prior statements stand. (CSNNE)

“I definitely don’t have [the playbook] down like I need to, so I try to [study] it quite a bit. Did a little bit today. I need to keep at it to know it like the back of my hand,” he said. “It’s a job so at the end of the day, you’ve got to do whatever you’ve got to do to be fully prepared to go out there. That’s what I have to continue to work on.”

With each game, Johnson feels more comfortable on the court. He is finding the balance between playing with his instincts and playing within the Celtics system.

“I would say it’s about half and half,” he said. “It’s a lot of mental stuff — defensive assignments, knowing all the offensive plays — but at the same time you have to let your instincts take control and just be ready to play. In a split second you’ve got to make a play on the ball and or block a shot.”