Geoff Burke/US Presswire

Jared Sullinger has put together a solid start to his rookie campaign.WALTHAM, Mass. -- Part of the reason why Jared Sullinger has delivered such a solid rookie campaign through the Celtics' first 17 games is because he hasn't settled on accepting the successes he has had up to this point.

Merely fitting in and not looking like a rookie among a host of veteran players has been an accomplishment in itself, but factor in the production -- he's averaged 7.2 points and 5.0 rebounds on 48 percent shooting over his last five games, for example -- and it's clear that Sullinger is steadily finding his NBA legs.

Ask him about hitting an early season stride, though, and he'll quickly brush aside the suggestion. He's more interested in discussing the things he can still do better.

"I'm making strides, but at the same time, I'm a rookie," Sullinger said after Monday's practice. "As a rookie you always have ups and downs. A lot of people think I'm playing well, but there's things I can do a lot better to help this basketball team out.

"I've still got to play with more confidence. Sometimes I'm hesitant. Sometimes I go back to things that I did in college that doesn't work at this level, and [head coach] Doc [Rivers] always reminds me of that. And so, I've just got to get better at being a pro."

Some of Sullinger's growing pains are beyond his help. He's already endured a host of questionable foul calls that simply are a part of the rookie package. While Rivers and and his staff have preached fouling less to Sullinger -- one assistant jokingly yelled, 'Stop fouling!' at Sullinger as he was being interviewed -- he's bound to pick up his fair share of ticky-tack calls all season.

One part of his game that Sullinger has shown more confidence in of late has been his jump shooting. While rifling off a 17-footer was a rarity earlier in the season, it's becoming a more common sight. Sullinger's been encouraged to take those shots more, and even works with Rajon Rondo on pick-and-pop scenarios after every practice.

"I mean, Doc tells me to shoot the open shot, so that's what I do," Sullinger said. "When I'm open, Rondo, everybody's telling me to shoot the shot, so, I'm just shooting it with a lot of confidence."

Rebounding has been Sullinger's primary focus since the opening day of training camp (his defensive rebound rate of 19.4 percent is second on the team only to Kevin Garnett's lofty 26.7 figure), and, as it turns out, some of the college tendencies he's trying to shake fall into that department.

"I mean, sometimes, effortless boxouts. I can't do that at this level," Sullinger said. "People are too long, too athletic, and just all the little things count. Once I get that down, I think I'll be a pretty good pro."

Sullinger's chances of succeeding in the NBA will always be bolstered by the natural instincts he has for the game. Much was made of his high basketball IQ at the start of the season -- Rivers, Rondo, and Garnett all openly acknowledged it -- and his feel for the game falls in line with that. Whether it's kicking the ball out of a double-team on the box to an open shooter, or zipping a pass from the elbow to an open Paul Pierce on the block, Sullinger has already demonstrated a knack for making plays that not everybody makes. That talent alone will help to navigate him through the rest of his inaugural season.

"You've got to have a certain feel for the game," Sullinger admitted. "That's why everybody talks about my feel for the game, my IQ, and sometimes those quick plays and quick passes always play into the role of IQ, and so what I see is what I do."