NEW YORK — When Kyrie Irving misfired again in his attempt to seal another Celtics win in the fourth quarter, he pursued the rebound and wrestled the ball away from 6-foot-8-inch DeMarre Carroll, who fell to the floor.

Irving quickly flicked the ball to rookie Jayson Tatum in the left corner.

The result? Swish.

“Oh yeah, he’s supposed to [hit that shot],’’ Irving said casually. “He better make it, wide open in the corner. Rookie or not, he better make the shot. Step in with confidence.’’

That three with 45.7 seconds left would cap a 5-point run by Tatum down the stretch as he catapulted the Celtics to a razor-thin 87-85 victory over the Brooklyn Nets at Barclays Center.

Before that pivotal 3-ball, Tatum soared for a one-handed hammer jam to give the Celtics an 84-83 lead with 1:16 left. Shooting sub-40 percent and again missing numerous 3-pointers, the Celtics were flirting with ending their unofficial first half with a disappointing loss to the less talented but hard-working Nets.

Tatum’s jumper gave the Celtics a 4-point lead but they missed on a defensive rebound and allowed Joe Harris to score on a tip-in with 36.9 left. Irving tried again to seal the game but he missed a 12-footer, giving the Nets the ball with 18.7 seconds to play.

Spencer Dinwiddie, who had beaten the Celtics off the dribble all night, tried again but rookie Semi Ojeleye met him at the rim with a hard chest bump and forced a miss. Harris’s putback was blocked by Irving out of bounds.

On the game’s final sequence, Ojeleye again used his muscular build to force Rondae Hollis-Jefferson into a fadeaway miss, and after two Nets batted the ball against the backboard, Hollis-Jefferson’s putback hit the front rim.

The Celtics limped away from Brooklyn with a sixth consecutive win after their Christmas Day loss to Washington, and now have one game in the next 10 days — a Jan. 11 matchup with the 76ers in London. The Celtics had been pushing themselves through the most games of any NBA team, anticipating a chance to get some much-needed practice time. What’s more, the Celtics prevailed against the Nets without starting center Al Horford, who missed the game with what the team listed as left knee/calf soreness.

“It’s a great way to finish before we head to London, so this was good for us,’’ guard Marcus Smart said. “It was real physical out there. The game was getting out of hand, to a certain extent. Especially on a back-to-back, that’s hard.’’

After missing 30 3-pointers in Friday’s win over the Timberwolves, the Celtics missed 13 out of 18 Saturday and another seven free throws. They couldn’t get any offensive flow and missed countless open looks. Irving missed 15 shots, Tatum nine, Aron Baynes nine, Smart 10.

But when the Celtics needed a boost, Tatum warmed up with a layup for a 4-point lead with 5:43 left and after Smart hit a jumper and a free throw, Tatum soared to the basket for his third dunk of the night. The Celtics-heavy crowd in Brooklyn went into a frenzy after the jam.

Tatum seemingly played upset after a tough foul call in the second period and began playing with an attitude. After the game, he returned to his quiet ways, refusing to acknowledge that he was angry.

“Determined,’’ he said. “It’s an emotional game and sometimes it brings the best out of you and sometimes that’s what you need to get over that hump.’’

It capped a marvelous first half of the season for the third overall pick, taken with one of the draft picks the Celtics acquired from the Nets in the Paul Pierce/Kevin Garnett trade and then swapped with the 76ers. He has shown the ability to take over games and has no hesitation with scoring against veterans.

On Saturday, he impacted the game defensively, finishing with a career-best six blocked shots. He was the first Celtics rookie to record that many in a game in four years and his length bothered the veteran Carroll, who missed 10 of his 13 shot attempts.

Celtics coach Brad Stevens has been reluctant to laud his 19-year-old rookie for fear of Tatum becoming complacent, but he also has no hesitation calling plays for him in critical moments.

“Those two plays he would have made right when he got here because he’s not scared of the moment, never has been,’’ Stevens said. “He’s gotten better in a lot of ways. But ultimately, he has a lot of ability, too.’’

Tatum is third on the team in scoring (13.9 points per game), second in blocked shots, along with 46.3 percent shooting from the 3-point line. Those two shots in the final 1:16, along with some stellar defense in the final seconds, saved the Celtics from what would have been a difficult loss.

“It would have been, excuse my language, a [expletive] plane ride to London if we didn’t get out of here with a win,’’ Irving said. “We probably would have been at practice [Sunday]. For us as a young, developing group to will ourselves to that win, there’s some games where we’re not going to necessarily score 90 points. On the flip side, we can hold teams to under 90 points, so we’ll always give ourselves a great chance to win if we’re playing at a high level.’’

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.