ORLANDO, Fla. -- Making his Celtics debut, rookie big man Jared Sullinger scored 14 of his game-high 20 points in the second half of Monday's summer league opener against the Oklahoma City Thunder to pace his team to a 73-65 triumph at the Amway Center.

"In the first half, I wasn't trying to overtake the game and make everybody want to focus on me," said Sullinger. "I was trying to make sure everybody was getting a feel. In the second half, it felt like I just tried to score the basketball."

Sullinger, who slid to the Celtics at No. 21 on draft day after concerns about a bulging disc in his back, showcased his all-around game Monday, able to muscle in baskets in traffic or step out and hit from beyond the arc. Sullinger finished 6-of-12 shooting (and 7-for-7 at the charity stripe) while adding six rebounds and a block over 24:08.

Sullinger said he won't be discouraged by giving up size at the NBA level.

"You just gotta play your game," he said. "You can’t change the game for someone that’s long or athletic. You have to be decisive with your movement. The more you do that, the better chance you have of putting the ball in the basket."