The dominant big man has been a staple of the NBA since, well, there has been an NBA. From Mikan to Russell to Wilt to Olajuwon to Ewing to the Admiral to Shaq, centers capable of taking over games at both ends of the court have been the most prized commodity in a league where even the little players generally tower over spectators of average height.

But with aging Shaquille O'Neal on his last tree-trunk legs and Yao Ming out again with a chronic leg condition that imperils his career, the last of the traditional power players, the Orlando Magic's Dwight Howard, finds himself on the endangered species list. Oh, sure, there are still rosters with 7-footers. They just don't rule the floor as they once did.

The 76ers' 108-97 win over the Houston Rockets at the Wells Fargo Center last night was emblematic of the changing face of the 21st-century NBA, where low-post play increasingly has been replaced by motion offenses and centers who don't station themselves under the basket nearly as much as did their gargantuan predecessors.

Sixers center Spencer Hawes, at 7-1 and 245 pounds, was the tallest player on the court last night. But he wouldn't have been had the Rockets' Yao, one of the biggest players ever to take up space in the paint at 7-6 and 310 pounds, been available to play. Yao, however, hasn't played all season with a stress fracture in his left ankle, and he again is talking retirement.

Hawes, a third-year player acquired from Sacramento before the season in a trade that sent Samuel Dalembert to the Kings, knows what it's like to be the guy always looking up during individual battles with Yao. He said his role is different going against a Houston team minus the Chinese giant.

"The base of their system is still the same, with the cutting and the high-post play," said Hawes of the Rockets. "But they push the ball a lot more and rely more on guard play than they did when Yao was in there.

"For me, personally, trying to defend him is one of the biggest challenges I have. You'd rather not have to deal with a 7-6 guy who's that good. But [6-9 Luis] Scola and [6-6] Chuck Hayes do a good job of filling in for him."

With 12 points last night, Hawes has now scored in double figures in 11 of the last 23 games, including a season-high five straight.

Sixers coach Doug Collins said there always will be a need for talented big men in the NBA, which is why he's come to rely on Hawes more and more of late. But he understands that the role of the traditional center is changing, part of the natural evolution of the game.

"That size really helps you at the end of the game," said Collins, who has given Hawes - a decent perimeter shooter - more freedom to slide outside and stick the 15-footer. "There's no hesitation on his part to shoot now. When he catches it, he can shoot it. If it's a good shot, take it. Let it go."

Of the Yao-less Rockets, Collins said, "They're a much more uptempo team now. When he's in there, they play through him in the halfcourt.

"Defenses have become so sophisticated, and to be a big man down in the post is to take a pounding every night. It takes a lot out of you. But when you can slide out and shoot that 15-footer, it forces defenses to rotate out a little bit further."