Dallas ? Before he was waived and moved on as the No. 3 overall pick in the NBA Developmental League draft, Darvin Ham imparted some wisdom to the Dallas Mavericks that they need to heed tonight against the Houston Rockets.

Ham’s message was to pay particular attention to a new and improved Yao Ming.

Not that overlooking the biggest player in the league is possible, but Ham’s point is that Yao is not the same movable object that he was earlier in his career. While Yao and Tracy McGrady still have to prove they have moved the Rockets into the NBA’s elite with a healthy season and playoff success, it is Yao’s play that suggests new coach Rick Adelman’s team is to be taken seriously.

All it took to convince Ham was the Mavericks’ preseason visit to Houston.

“The one thing that impressed me in guarding him is that he’s not passive at all anymore,” Ham said. “He is taking the fight to you. There was a time a couple years ago in Detroit when I had him for four or five possessions and you could shoot him an elbow or get physical on him and he’d be leaning over or complaining to the refs.

“Now, he’s so bottom heavy, when he gets post position, you’re not going to move him. He understands now. He knows how big he really is. If they can be consistent with that and go through him, they’re going to have a lot of success.”

Gone are the days when you could stick a Raef LaFrentz on Yao and watch the 7-6 center struggle. The Rockets bring a 3-0 start to the season into Monday night’s game, which will be a nice test for the Mavericks.

So far, they’ve beaten a Cleveland team that was unready for the season, lost at Atlanta to a youthful, exuberant Hawks team and blasted short-handed Sacramento, a team that’s not going to be very good even when its healthy.

So Monday night is a much stiffer challenge, though the Rockets still haven’t gotten past the first round of the playoffs in the Yao-McGrady era.

Yao is averaging 19 points and 10.3 rebounds. The only time the Rockets beat the Mavericks last season was when Yao had 36 points. When McGrady led the Rockets in scoring, they were 0-3 against the Mavericks.

“They’re a terrific team,” Avery Johnson said. “A lot of people have them as favorites to win the championship this year. For us, it should be a pretty big test for us because a lot of people are really talking about their potential.”