While stringing together the second-longest winning streak in NBA history, the Houston Rockets have been dogged by questions about the quality of their opponents.

A win on Tuesday night could help them eliminate any remaining doubts.

After beating one of the league's top teams to take sole possession of first place in the Western Conference, the Rockets look to answer another challenge as they go for their 23rd straight win against the league-best Boston Celtics at the Toyota Center.

Houston (46-20) hasn't lost since falling to Utah on Jan. 27, snapping a four-game run. The Rockets now only trail the 1971-72 Los Angeles Lakers for the longest win streak in league history - that team won 33 in a row en route to the NBA title.

However, some are unimpressed by Houston's run because the Rockets haven't been tested by any elite teams. They have two wins over Cleveland and New Orleans, and one apiece over Dallas and the Lakers, but the majority of the other victories have been deemed less than remarkable.

A win over the Celtics (53-13) may finally give the Rockets' run some legitimacy in the minds of skeptics.

"It's going to be a challenge, it's going to be a tough game for us," Houston guard Tracy McGrady said. "But we're capable of winning it."

Boston might be just as confident after its comeback victory over San Antonio on Monday night. The Celtics trailed by 22 early in the second quarter, but rallied for a 93-91 win.

"A lot of teams may have buckled," said second-year point guard Rajon Rondo, who scored 20 points. "But we knew we had to execute. Continue to get stops on defense and we knew the game would change for us, and it did."

The Celtics, who are 13-2 in the second half of back-to-back games, have won 12 of their last 13 overall and already have more victories than they've had in any season since 1990-91.

The Rockets, though, are also coming off a significant victory, beating the Lakers 104-92 on Sunday to move atop the West. It was their 11th double-digit win in their last 13 games.

"This was really all about how good the Rockets are," McGrady said. "This is what this game was about, the Lakers coming in here at the top of the Western Conference. This game determined where we are. We answered those questions, we took on that challenge and we're standing alone."

McGrady was held to 11 points on 4-of-16 shooting, but the Rockets got career highs of 31 points and eight 3-pointers from point guard Rafer Alston and a tremendous defensive effort on Lakers star Kobe Bryant by Shane Battier in the victory.

The balance is particularly important for a Rockets team that's playing the rest of the season without All-Star center Yao Ming. Houston has already won 10 straight without their leading scorer and rebounder, who's sidelined with a stress fracture in his left foot.

"We're getting it every night from different guys," said Alston, averaging 15.7 points, 6.6 assists and just 2.0 turnovers during the streak. "We can call a play for Tracy, but everyone is still involved in that play. We're all moving, the ball's hopping. That says a lot about us and our team and how everyone has turned their games up."

The Rockets are still under a lot of pressure to continue their run as only six games separate the top nine teams in the West.

"Even though we've won so many games in a row, we have to keep winning," Alston said. "We're only like 1 1/2 games ahead of a couple of teams. If we keep winning and if other teams continue to lose, we widen the gap. So, every game is important until we have a three- or four-game cushion on these guys."

Boston, which has already clinched a playoff spot in the less-competitive East and the Atlantic Division title, could be without Ray Allen (left ankle) for the third consecutive game. Celtics coach Doc Rivers said Monday he doubted Allen would be ready, and added that the eight-time All-Star is more likely to return Thursday in Dallas.

Boston won its first meeting with Houston 97-93 on Jan. 2 behind 26 points from Kevin Garnett. Alston had 18 for the Rockets, who were playing without McGrady because of a knee injury.

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