HOUSTON, March 5 (Ticker) -- Tracy McGrady's bad back could only mean bad things for the Houston Rockets.

McGrady left late in the third quarter after appearing to aggravate a nagging back injury that has hampered him for much of the season in the Rockets' 102-84 victory over the Portland Trail Blazers.

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After scoring 18 points on 7-of-18 shooting, McGrady walked gingerly to the locker room with 1:11 left in the third quarter and did not return. The Rockets have gone 1-13 without their All-Star in the lineup this season.

"It's a little tight, it's sore," McGrady said. "I came down on my tailbone. I'm going to get treatment (Monday). I'm going on the trip (to Minnesota on Tuesday) but (my playing) status is unknown."

Rockets coach Jeff Van Gundy realized the injury could be serious.

"When he's come out of a game, he's sat out (more games) in the past," he said. "He doesn't take himself out lightly. But we expect to play well, and win, regardless."

Losing McGrady for any stretch would be a devastating blow for the Rockets (27-33), who are four games behind the Los Angeles Lakers for the Western Conference's final playoff berth.

"If it's his back again, it's not good," said Houston guard David Wesley, who did not see McGrady walk off the court. "We need him healthy and ready to play."

"We need to do like we did in the Golden State game," Rockets center Yao Ming said of the team's lone victory this season without McGrady. "Everybody do something more."

Yao, who was having a big game before McGrady went down, collected a season-high 32 points and 13 rebounds to pace Houston, which has beaten Portland nine straight times.

"I'm not surprised when (Yao) plays well," Van Gundy said. "He is prepared every day. He works hard every day. He's one of the few guys who doesn't need outside motivation. He is without question the best regular-season center in basketball."

The 7-5 Yao fared well 7-3 Korean Ha Seung-Jin for a brief stretch in the third quarter, when the Rockets used a 22-8 run over the final 6:03 to turn a tight game into a 76-62 lead.

"Yao was too much for us," Portland coach Nate McMillan said. "We tried doubling him and playing him straight up and he had an answer for whatever we put on him. When we double-teamed him, he knocked down his shots."

Yao scored 10 points in the burst and 17 in the quarter. Ha collected four fouls in five total minutes.

"The first half, those weren't my shots," said Yao, who was just 3-of-13 before halftime. "At halftime our coach said, 'If you don't want to play hard, sit on the bench.' That scares people. The second half, everybody worked hard. We finished the game the way we know we can."

"Every game I start by telling him to dominate," Wesley said. "He's done that. He's a powerful force down there."

The Rockets struggled offensively in the first half but came alive after the break, shooting 60 percent (21-of-35) and scoring 63 points. They shot just 34 percent (16-of-47) in the opening half.

"That's fun to do, when you go out and play well, even if it's only for three quarters," Wesley said.

Steve Blake scored a career-high 23 points and Zach Randolph added 15 for Portland, which lost for the 12th time in 15 games.