McGrady sat out with a sore left shoulder that's bothered him for more than a week, but the Rockets didn't miss him, handing Seattle its 11th staright road loss.
Rookie Luis Scola had 13 points and 12 rebounds, Luther Head started for McGrady and scored 16 and sharp-shooting reserve Steve Novak added a career-high 17 points as Houston kept pace with first-place New Orleans in the tightly packed Western Conference playoff race.
"I'm really proud of our bench guys," Houston coach Rick Adelman said. "I mean, they just stepped up. The guys that we needed to step up off the bench did a good job."
Former Texas star Kevin Durant scored 26, Nick Collison grabbed 15 rebounds and Earl Watson added 16 points and eight assists for the Sonics, who've lost seven straight meetings with Houston and 18 of their last 20 games overall.
"I didn't like the way we played," said Seattle coach P.J. Carlesimo. "We played like a very tired team, much more on defense."
The Rockets had lost 12 of the previous 13 games they played without both McGrady and Yao Ming in the starting lineup since the two became teammates before the 2004-05 season. Yao has been out since late February with a broken foot, but Houston was playing its first game this season without either All-Star.
No problem. The Rockets shot 53 percent (39 of 74) and outrebounded Seattle 47-35 to win for the 33rd time in their last 39 games.
"For any team to be able to be successful in the playoffs, you've got to have guys that are going to be able to come in and play and have depth," Novak said. "We've done a good job of that all year."
Novak sank a career-high five 3-pointers and Scola recorded his eighth double-double of the season as Houston won for the 20th time in its last 22 home games. The Rockets stayed two games behind the Hornets in the race for the No. 1 spot in the West.
"It was a huge victory for us," Scola said. "If we lose, Phoenix and Utah and everybody is going to get over us, we would lose home-court advantage and it would make things much more difficult."
Head scored eight of Houston's 11 points and the Rockets built an early nine-point lead. The Sonics missed 13 of their first 18 shots and trailed 19-10 after Alston's second 3-pointer.
The Sonics finished the quarter with a 16-2 run, capped by Damien Wilkins' banked-in 3-pointer with 1.8 seconds left. But Seattle went cold again in the second quarter and Novak swished two 3-pointers during a 15-2 spurt that put Houston up 36-28.
The Rockets led 46-37 at the break, holding Seattle to 32 percent shooting (16 of 50) for the half. Durant had 13 in the half, but was only 6-for-17 from the field. The Sonics missed 19 of 24 shots in the second quarter.
"We just can't hit shots against this team," Durant said.
Scola had a dunk and two layups during Houston's 14-0 run in the third quarter. He passed to Alston cutting down the lane for another layup that put the Rockets up 65-44 with 6:02 remaining in the quarter.
Scola had 10 points, six rebounds and three assists in the quarter and Houston led 75-59 heading to the fourth. Novak sank another 3-pointer 2 minutes into the final quarter as the lead swelled back to 20.
Adelman used all reserves the rest of the way as Houston reached its highest win total (53) since the 1996-97 team finished the regular season 57-25.
"We want to continue to stay in good rhythm," Alston said. "We just want to finish the season on a winning note and work on the things we need to work on."
Seattle G Luke Ridnour bruised his left calf late in the second quarter trying to defend Carl Landry. He came out for the second half with a wrap around the injury and returned with 1:19 left in the third quarter. ... Rockets F Shane Battier bruised his left foot with 45 seconds left in the first quarter and sat out the rest of the half. He started the second half, played 7 minutes, then came out for good late in the third quarter. Team officials said Battier would have an MRI exam on Thursday and was questionable for Friday's game against Phoenix. ... The Rockets are 49-4 when they lead after three quarters.