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DALLAS -- Now that it's playoff time, the Dallas Mavericks know they're going to need to play the smothering defense they showed in the third quarter of their season finale.

And if Dirk Nowitzki can keep up his shooting touch, they might really have something.

Nowitzki scored 12 of his 32 points in the decisive third quarter, leading the Mavericks to a 121-89 victory over the Hornets on Wednesday night. Then came a few hours of waiting for both teams to learn their seeds and first-round foes.

Dallas wound up No. 3 in the Western Conference, facing Portland in the opening round. The Mavs had a chance to move up to No. 2, but the Lakers held onto it by beating Sacramento in overtime later Wednesday.

"We'll be ready," Nowitzki said. "It should be a fun run."

New Orleans landed seventh, and will face the Lakers. The Hornets could've dipped to eighth, but Memphis was crushed by the Clippers.

"We're in this position because we've done some things well and we can't lose sight of that," New Orleans coach Monty Williams said.

Considering all the scenarios, both teams came in focused mostly on trying to feel better about themselves going into the postseason. Dallas had lost nine straight to West playoff teams, and New Orleans had lost its last two games by 12 and 22 points.

The Hornets had the better start, leading 61-58 at halftime and making 57.5 percent of their shots. But the Mavericks took it to them in the second half.

Realizing defense is going to make or break them in the postseason, the Mavs ratcheted up the intensity. Tyson Chandler protected the rim and DeShawn Stevenson brought his toughness to the perimeter. Dallas repeatedly knocked down Chris Paul and let the Hornets know they weren't going to get any more easy baskets.

They didn't get many more baskets, period.

New Orleans scored only 13 points in the third quarter, just one more than Nowitzki. The Hornets wound up scoring just 28 in the second half, letting the Mavs roll to their most lopsided win of the year.

"The second half is a blueprint for how we're going to have to play in the playoffs -- rugged defense and moving the ball," Dallas coach Rick Carlisle said. "Our activity on defense was outstanding."

While the Hornets didn't get the feel-good performance they wanted, at least they got some rest. No starter played more than 26 minutes.

Jarrett Jack led New Orleans with 22 points. Marco Belinelli had 14 points and Paul had seven points and eight assists.

"We let our guard down a bit in the second half," New Orleans coach Monty Williams said.

Paul preferred to look ahead to the playoffs. Despite going in following three straight crushing losses, he remains optimistic.

"These 82 games don't mean too much," he said. "We know what we're capable of."

Nowitzki made 10 of 21 shots on his way to his most points in nearly a month. He was four shy of his season best when he went out for good with about 6 minutes left. His 32 points came in 31 minutes.

J.J. Barea scored 14 points, Jason Terry had 13 and Jason Kidd had 12 points and eight assists.

Shawn Marion added 10 points, eight rebounds and four assists. He also joined Hakeem Olajuwon, Karl Malone, Kevin Garnett and Julius Erving as the only players with 1,500 steals and 1,000 blocks.

Carlisle made the surprise move of starting Stevenson over Roddy Beaubois, the second-year guard who'd started the last 26 games and is considered a big piece of the club's future.

"I just thought it was time to give that another look," Carlisle said. "Things change."

Beaubois came off the bench -- then sprained his left foot in the second quarter and didn't return. X-rays showed no break, which is significant because a fracture in that foot kept him from making his season debut until Feb. 16. Even if he's OK to play, it looks like Stevenson may be back in the starting lineup going into the playoffs.

"When D-Steve's in the starting lineup, we feel like we can put him defensively on anybody and switch back and forth from the point guard," Terry said. "He's a veteran guy and knows what needs to be done and that helped us out big time tonight."

Peja Stojakovic was not with the Mavs for personal reasons. He's expected back for the playoff opener.

Game notes

Before tipoff, Dallas backup center Brendan Haywood spoke to the crowd, saying, "Y'all are the best fans. We expect the same thing in the playoffs. Actually, the playoffs start tonight." ... The Mavs clinched at least the No. 3 spot with about three minutes left, when Oklahoma City lost. ... New Orleans knew it would be seventh or eighth, but had four potential first-round foes. ... It was the 399th consecutive regular-season sellout for Dallas, tops in the NBA.