Dallas Mavericks forward Dirk Nowitzki (R) grabs a rebound as Portland Trail Blazers guard Brandon Roy looks on during the first quarter of their NBA basketball game in Portland, Oregon on March 15, 2011. Mavericks were beaten 101:104 by Trail Blazers in the regularseason game. (Xinhua/ Reuters Photo)

Brandon Roy's ongoing process for dealing with his knees is not to get too excited when things go well - as they did against the Mavericks.

Roy came off the bench to score 21 points, including a key jumper with less than a minute to go, in Portland's 104-101 victory against Dallas on Tuesday night.

Roy, a three-time all-star, had arthroscopic surgery on both knees in January because of too little cartilage, a condition that will likely bother him the rest of his career.

Since the surgery, he has come off the bench and his minutes have been closely monitored.

"It's a process. I try to stay even keel with everything going on," he said. "Tonight, I felt great."

The Blazers led 100-94 with 3:50 left, but Jason Terry's basket narrowed it to 100-99. Roy hit a pair of free throws before a pull-up jumper that made it 104-99 with 47 seconds left.

Dirk Nowitzki hit a pair of free throws, but after a timeout with 8.8 seconds on the clock, he missed a 3-point attempt from the corner and time ran out for the Mavericks.

"That's the best I've seen him this year," coach Nate McMillan said of Roy, who went on his own personal 10-4 run for the Blazers midway through the second half.

Nowitzki finished with 28 points and 11 rebounds for Dallas, which shot 59.7 percent.

LaMarcus Aldridge led the Blazers with 30 points and eight rebounds. Wesley Matthews added 18 points.

The Mavericks had a tense moment in the first half when Nowitzki left the court with what appeared to be a shoulder injury. He returned to the bench a short time later, however.

Dallas made its first 10 shots and didn't miss until Brian Cardinal's failed 3-point attempt with 3:25 left in the first quarter. The errant shot earned applause from the Rose Garden crowd. The Mavs shot 73 percent in the first quarter.

Dallas led by eight points early, but Portland narrowed the gap to 24-21 on Aldridge's dunk. Portland briefly took the lead when Matthews' 3-pointer made it 45-43. But Dallas quickly reclaimed the lead on Terry's 3-pointer and the Mavericks were up 56-53 at the break.

The Mavericks extended the lead to 71-62 on Tyson Chandler's dunk. The Blazers kept up the pressure and Aldridge tied it at 76 with a turnaround jumper late in the third quarter. Portland took a 78-76 lead on Roy's layup.

It was the first of 10 straight points for Roy that put Portland up 86-80 early in the fourth quarter.

"He made some tough shots. He looked like the Brandon Roy of old," Nowitzki said. "If he shoots the ball like that, they've got two legit go-to guys with Aldridge, who is playing phenomenal, and him. They're going to be tough to beat in the playoffs, whoever they play."

McMillan said Roy's effort against Dallas doesn't mean his "process" in coming back this season will change.

"We've talked to him about his minutes. He's feeling good with the minutes that he's been getting and we need to keep him there," the coach said. "That's working. We haven't had any setbacks."

Roy said half of what he's dealing with is mental.

"I've got to challenge myself to push through, and know that my body's OK," he said.

The Mavericks were without Brendan Haywood, who was sitting with lower back stiffness. Peja Stojakovic missed his fourth straight game with a stiff neck.

The Blazers switched things up by starting Gerald Wallace in place of Marcus Camby. Wallace, an all-star last season, came to the Blazers in a trade with Charlotte at the deadline last month.

Camby had arthroscopic knee surgery in January and his minutes have been limited since his return. McMillan did not say whether the change was permanent.

Portland was home after two straight losses on the road. The Mavericks were coming off a 96-91 loss at home to the Lakers on Sunday.