DALLAS — If the Dallas Mavericks ever figure out the third quarter, they might be on to something in their quest to rejoin the elite in the Western Conference.
Until then, they'll be dealing with some frayed nerves.
Chandler Parsons scored 29 points, including a key 3-pointer to help Dallas hang on after going up by 30 before halftime for the second time in two home games, and the Mavericks beat the Boston Celtics 118-113 Monday night.
"It's concerning," said Parsons, who also won a key jumpball with Boston within three in the final minute after trailing by 31 in the second quarter. "I love how we never give up after we give up the lead. But we can't allow these teams to keep coming back in and cutting the lead."
Jeff Green led the Celtics with 35, and Avery Bradley had a career-high 32 but missed one of three free throws with a chance to tie with 39 seconds left after getting fouled on a 3-pointer by Monta Ellis.
"We shot ourselves in the foot in the first half the last two games," said Green, whose team trailed Houston by 19 at halftime in a loss Saturday. "By the end we were out of gas. We can't allow teams to be the aggressor the first 12 minutes. That's what happens."
Dirk Nowitzki scored 27 for the Mavericks, who shot 73 percent in the first quarter and had at least 66 points at halftime for the third straight game, all wins since a season-opening loss at San Antonio.
But Dallas cooled off and couldn't shake Boston the way it did Utah after going up by 30 before halftime and losing more than half the lead in an 18-point win in the home opener.
The Mavericks have been outscored in the third quarter of all four games, three times by double digits. New Orleans scored 37 while wiping out most of a 17-point deficit on Saturday. The Celtics hit eight of their first nine shots in a 38-point third quarter.
"To continue getting the leads, that would be great," Dallas coach Rick Carlisle said. "If we can keep doing that, we will deal with the other stuff. We will get it solved."
Parsons had a 3-pointer and an easy layup after a turnover to push Dallas' lead to 114-104 before the Celtics scored seven quick points to get close again in the final minute.
After Bradley missed the second of three free throws with a chance to tie, Ellis put Dallas back up by three at 116-113 with a driving layup.
The Celtics had another chance to get even when Green missed a 3 with 20 seconds left, and Parsons won the tip with Jared Sullinger after they ended up in a jump ball following a mad scramble on the floor.
The first time Boston cut its 31-point deficit to 3 in the fourth quarter, it came on a 3-pointer by rookie first-round pick Marcus Smart, who played at a Dallas-area high school and had quite a cheering section for his first pro game close to home. Several dozen students from Marcus High School in nearby Flower Mound wore T-shirts that read, "We Are 4 Marcus," with his No. 36 inside a shamrock.
"Some of the guys played on the JV team when I was on the varsity. It makes me feel old," said the 20-year-old Smart, who got a loud ovation when he came into the game and finished with seven points, six rebounds and three assists.
Celtics: Boston was 11 of 31 from 3-point range after making just 1 of 25 from beyond the arc in Houston. Bradley was 4 of 6 and Green was 5 of 12. ... Rajon Rondo had team highs with 15 assists and nine rebounds. ... Bradley scored 14 points in the fourth quarter.
Mavericks: Tyson Chandler had his first double-double since returning to Dallas with 10 points and a game-high 12 rebounds. ... Parsons and Nowitzki combined to go 8 of 9 on 3-pointers. ... Forward Al-Farouq Aminu left the game in the second quarter with a left knee injury. Carlisle said he didn't think the injury was serious.
Celtics: Return home to face Toronto on Wednesday after a two-game Texas swing opened the road schedule.
Mavericks: Get two days off before their first back-to-back on the road at Portland and Utah.