Wizards forward Antawn Jamison left in the first quarter with a right knee injury and did not return.
Jamison's leg appeared to buckle while playing defense midway through the first quarter, and he had to be helped to the locker room by teammates. A team spokesman at first said the knee was sprained, but later changed the diagnosis to a less serious-sounding strain.
Jamison will have an MRI and be evaluated on Wednesday. The two-time NBA All-Star averaged 21.4 points and 10.2 rebounds in 79 games for the Wizards last season.
Wizards center Brendan Haywood missed the game with a sprained right wrist, which he will have examined by a hand specialist in New York City on Wednesday. Haywood sustained the injury last week at training camp.
The Wizards are already without high-scoring guard Gilbert Arenas, who's expected to miss several months with a left knee injury.
Dallas shot 52 percent from the field and built a 55-40 halftime edge behind Nowitzki's 10 points.
Nowitzki's layup and 3-pointer on consecutive possessions midway through the third quarter stretched Dallas' advantage to 70-51, and the Mavericks went on to lead by as many as 36 points in the final quarter.
Dallas' Josh Howard, who finished with 15 points, was greeted by a mixture of cheers and boos from the crowd when he was introduced with the starting lineup following a controversy-filled offseason.
In a video posted on YouTube that was widely viewed on the Internet, Howard was shown at a summer charity flag football game disrespecting the national anthem. Howard apologized on the first day of training camp.
Howard held his hand over his heart while the national anthem was sung prior to the game.
Howard had another off-court incident during the offseason when he was arrested in July after police said he was drag racing at 94 mph in a 55 mph zone.
Last season Howard was criticized for saying in a radio interview during a first-round playoff series against New Orleans that he occasionally smokes marijuana. Later in the same series, he drew the ire of then-coach Avery Johnson by throwing himself a birthday party after a Game 4 loss to the Hornets.
New Mavericks coach Rick Carlisle said he anticipates a strong season from Howard, who averaged 19.9 points and seven rebounds in 2007-08.
"I expect him to play well," Carlisle said. "As far as any other stuff [adverse fan reaction to Howard], I don't expect much if any of that. I think his [apology] was sincere and heartfelt ... As you progress through this business, your skin thickens a little."