Yao had 21 points and 12 rebounds in an 89-88 victory over the Blazers on Sunday night. Once his teammates were able to get him the ball inside, Yao was nearly unstoppable. When Portland tried to double him, that left someone else open.

"When Yao is scoring for us and gets a lot of touches, he's our foundation and we feel great every time he catches the ball because we know he commands so much attention that it's going to open up things for us," Rockets forward Shane Battier said.

While focused on Yao, the Blazers also made some crucial mistakes that cost them after leading 70-64 going into the fourth quarter.

Two obvious errors came with less than a minute to play. First, when a falling Joel Przybilla badly overthrew Steve Blake after rebounding Blake's missed 3-point attempt, the ball sailed into the backcourt. Then, with Houston leading 87-85, Portland's Brandon Roy drove to the basket and was called for an offensive foul when he ran into Chuck Hayes.

Portland was also hurt by giving up 10 offensive rebounds in the final quarter.

The victory moves Houston closer to advancing to the second round of the playoffs for the first time since 1997.

Portland has had trouble matching up with Yao the whole series. In Game 1, the Blazers had Przybilla play behind the 7-foot-6 center from China - which didn't work.

Portland seemed to find more success when Przybilla fronted him. A rarely used combination of Przybilla and rookie Greg Oden - both 7-footers - playing at the same time also tricked the Rockets in Game 2, Portland's lone win thus far.

But the Rockets adjusted to all of Portland's schemes to stop Yao, and took both of the next two games in Houston.

"I really thought he countered them pretty good," Rockets coach Rick Adelman said. "He didn't get in a wrestling match with them as much as he had the first couple games. To be honest, they got some fouls when he was trying to move across the lane, but I thought he was smarter at moving across the lane."

Yao is averaging 15.8 points and 10.5 rebounds through the first four games of the best-of-seven series. Luis Scola leads the Rockets with an average of 16.8 points. He's also averaged 7.5 rebounds.

The Blazers are making their first appearance in the playoffs since 2003. They set the goal of making the playoffs at the start of the season, but surprisingly clinched the fourth seed in the Western Conference and home-court advantage.

Home court could help Portland on Tuesday. The Blazers were 34-7 at the Rose Garden during the regular season.

Two-time All-Star Roy, a third-year player with no playoff experience, has the job of rallying his team for Game 5.

"I don't want anybody in our locker room to get down," said Roy, who had 31 points in Game 4 and is averaging 28.3 in the series. "I think this is a great experience. We're fighting extremely hard. There's just some minor things we have to improve on. And just going through this experience I think will help us in the long run."

Roy did not practice Monday afternoon because of flu-like symptoms, but he was listed as probable for Tuesday's game. A call to the Blazers to provide more details about his symptoms was not immediately returned.

LaMarcus Aldridge, who was averaging 16.5 points and 8.3 rebounds for Portland during the playoffs, also didn't practice Monday because of a right elbow strain. He was also expected to play in Game 5.

Notes: Rockets center Dikembe Mutombo, who sustained a career-ending injury in Game 2, underwent successful surgery Monday to repair a ruptured quadriceps tendon in his left knee.