DALLAS (AP) -- Ray Allen was sitting on the bench in the fourth quarter, arms crossed and a black shirt over his jersey. He was forced to watch James Posey take his place, just like he'd done the last few nights in Houston and San Antonio.
With 1:54 left, Allen finally got in. And with 31.7 seconds to go, he nailed the 3-pointer that capped the Celtics' dominant season over Texas teams.
Allen's go-ahead jumper sent Boston past Dallas 94-90 Thursday night, making the Celtics the first team to go 6-0 vs. San Antonio, Houston and Dallas since the 1999-2000 Milwaukee Bucks or 3-0 on a Texas road trip since the Sacramento Kings in November 2001.
"This feels good," said Allen, who'd missed three games with a jammed left ankle. "It's something for the rest of the NBA to watch."
Boston upped its NBA-best record to 55-13 while winning for the 14th time in 15 games. The Celtics ended a seven-game losing streak in Dallas and swept the season series for the first time since 1993-94.
Best of all for coach Doc Rivers was having his trio of stars back in the starting lineup -- and atop the stat sheet.
"It's good to see Ray back and healthy," Posey said. "That's what he does, make big shots. He's a big part of this team."
The Mavericks led for most of the second half, but couldn't pull it out at the end. That's been typical in this new Kidd era, with five of their losses by six points or less. They were coming off a 2-point loss to the Lakers, although in that one they had to claw back from a 25-point deficit.
"We're just right there in a lot of these games," said Jerry Stackhouse, who scored 17 points. "It's disappointing to keep coming up short."
Dallas needs to snap out of it soon with San Antonio coming to town Sunday. The Mavs had won five straight against losing teams before these back-to-back home losses, the first time that's happened all season.
"The energy was there," coach Avery Johnson said. "Some things didn't go our way, but we hung in there."
Allen scored 18 points in 29 minutes over the first three quarters and had to figure he'd be back in. But that didn't happen until 10:06 elapsed, his opportunity only coming when Kendrick Perkins fouled out.
Nowitzki made both free throws off Perkins' foul, putting Dallas up 88-87. Neither team scored until Allen swished his jumper from the left side.
"It was a play Doc drew up in the timeout," Allen said. "Stack fell and I got to the 3-point line. I shot it high so that if I missed, KG could go up for the rebound."
Nowitzki missed the chance for a tying layup, then Posey stretched the lead with a pair of free throws. A layup by Erick Dampier got Dallas back within two with 6.7 seconds left, but Garnett sealed it with two more foul shots.
The Celtics took 18 free throws in the fourth quarter. They took 17 over the first three quarters combined. Boston made 30 of the 35.
The accuracy from the line was needed because the Celtics shot only 34.5 percent from the field, dragged down by starting point guard Rajon Rondo going 0-for-7 and backup Sam Cassell going 1-for-9. Cassell played the entire fourth quarter, as did Posey, who was 4-of-5 with 12 points.
"Ray was rusty and Posey was phenomenal," Rivers said.
Neither team led by more than seven, which kept the intensity going up. Things got snippy in the fourth quarter, especially between Nowitzki and Garnett, although nothing ever escalated beyond tough play.
The first half was filled with spurts, from Dallas closing the first quarter on a 12-2 run to Boston opening the second on a 14-4 roll. The Mavericks enjoyed the final push, a 13-5 streak featuring a go-ahead three-point play by Nowitzki and a mad-dash layup by Kidd that sent them into the locker room ahead 48-46.
Boston remained at a one-Allen maximum, as Ray Allen's return coincided with Tony Allen sitting out with a bruised lower back. ... Nowitzki came into this game averaging 27.2 points per game against Boston for his career, his highest against any foe. ... By dropping Dallas to 29-6 at home, Boston takes over the NBA's second-best home record at 29-5. ... The Mavs had a season-high 12 blocks, topping the 11 in their previous game. ... Boston last swept the Texas Triangle in February 1987.