The Mavericks had their six-game winning streak snapped in a Sunday matinee at Madison Square Garden. The Boston Celtics arrived in Dallas with much bigger problems.

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Chuck Cooperstein recaps the Mavericks' weekend, including their trip to NY against Jeremy Lin. Listen

The Celtics have been contenders ever since they pulled off deals to acquire Kevin Garnett and Ray Allen, but Boston looks more like a lottery team right now.

Actually, the lack of depth in the Eastern Conference essentially assures the .500 Celtics a playoff berth, but it’ll be a brief postseason in Boston unless things get much better. The Celtics have lost five of their last six games, including two double-digit losses to the 11-22 Detroit Pistons and one to the 9-23 Toronto Raptors.

The Mavs, the NBA’s oldest team, are a surprising 7-3 in the butt end of back-to-back games this season. That record should improve Monday night, despite the familiar, respected name of the foe.

Records: Mavs (20-12); Celtics (15-15)

When: 7 p.m.

Where: American Airlines Center

TV: TNT

Radio: ESPN Dallas 103.3 FM; 1270 AM (Spanish)

What to watch: Will the Dallas defense bounce back after one of its worst performances of the season? Boston, even with Rajon Rondo and three 20,000-plus-point career scorers, have been a poor offensive team this season. They rank 26th in the NBA in scoring at 89.5 points per game. The Celtics are 2-13 in games in which they fail to score at least 90 points. Rondo could present problems for Shawn Marion and the Mavs, whose remarkable run of defending quality point guards came to a halt with Jeremy Lin’s 28-point, 14-assist performance Sunday in Madison Square Garden. However, there’s a chance that the NBA office could lock down Rondo, who might face a suspension after being ejected for tossing a ball at a referee during the Celtics’ Sunday loss to the Pistons.

Key matchup: Dirk Nowitzki vs. Boston power forwards: Nowitzki has traditionally torched the Celtics no matter who Boston uses to defend him. He has a career average of 27.0 points per game against the Celtics, his highest against any team. Boston might have to start third-stringer Chris Wilcox, as Kevin Garnett is dealing with personal issues that caused him to miss Sunday’s loss in Detroit and Brandon Bass has a sore left knee. Nowitzki, who blew by Garnett for a game-winning and-1 layup in the Mavs’ victory in Boston earlier this season, enters the game in a pretty good groove even by his Hall of Fame standards. He has 58 points on 19-of-31 shooting in the last six quarters.

Injuries: Mavs – G Delonte West (fractured right ring finger) is out; G Rodrigue Beaubois (personal reasons) is out. Celtics – PF Brandon Bass (knee) is questionable; PF Kevin Garnett (personal reasons) is questionable.

Up next: Los Angeles Lakers at Mavs, 8:30 p.m., Wednesday