At the beginning of the season, the center position was not a concern for either Stanford or Arizona, as the Cardinal had 7-foot-1, 245-pound sophomore Tim Young, and Arizona had 6-10, 265-pound Joseph Blair to take up the middle.

But as often happens in college basketball, things change.

Young was lost for the season and will redshirt after he suffered a bulging disk in his lower back in December. Blair departed soon after, put on academic probation following the Jan. 10 Arizona State game.

But the season must go on, and both teams have changed their offensive sets to make up for the hole in the middle. The No. 11 Wildcats (23-5 overall, 12-4 in the Pacific 10 Conference) have gone to a two- guard, three-forward set, while Stanford runs with three guards and two forwards. The beneficiary of the change for Stanford (17-8, 10-6) has been senior guard David Harbour, who has moved into the starting lineup and averages 9.2 points per game.

The two teams will get a chance to test each other's progress tonight at 8:30 at McKale Center.

Cardinal head coach Mike Montgomery said there have been bright spots for both teams in losing their big men.

"They had Blair, we lost Tim Young. It's the same thing," said Montgomery, whose Cardinal team has almost guaranteed itself no worse than a fourth-place finish in the Pac-10 and has probably qualified for the NCAA Tournament for the third time this decade. "It makes a very different team with more perimeter shots and more movement. That game gives more freedom. The ball doesn't have to go to a set person inside."

That switch is much easier if a team has the backcourt Stanford does. Junior point guard Brevin Knight and senior Dion Cross give the Cardinal one of the top guard combinations in the nation. Knight leads the team with 14.7 points and the Pac-10 with 7.4 assists, while Cross is a deadly shooter who averages 14.2 points and is ninth in the conference in 3-point shooting at 38.5 percent.

Arizona head coach Lute Olson said the pair resemble a couple of former UA players who made a formidable combination two years ago, Damon Stoudamire and Khalid Reeves. Olson said despite the praise heaped on the Cardinal backcourt, the Wildcat combo of Reggie Geary and Miles Simon would not back off.

"This one should be a real interesting challenge for Reggie and Miles because in most people's opinion the best guard combo in the league is at Stanford," Olson said. "That's something Reggie and Miles will want to challenge in this game."

"The biggest factor in guarding Brevin is keeping him in front of you," Geary said. "With his intensity, he is definitely the key to the team."

While the Wildcats have been able to spread the scoring load around in Blair's absence - six UA players average 9.5 points or more - Stanford has been more reliant on the triumvirate of Knight, Cross and senior forward Andy Poppink (14.5 points) for the majority of its offense.

Montgomery said one of the problems his team has faced of late € Stanford has lost three of its last four - has been offensive stagnation, as players will wait for a teammate, usually Cross, to make a play.

"I think it would be a good thing to guard Cross, but everyone's doing that," Montgomery said. "It has to be where we get everyone involved and create shots off movement."

This game will provide a contrast between Arizona, the conference's top-scoring offense with 81.6 points, and the Cardinal, the stingiest team in points allowed, with a 66.6 average.