ALBUQUERQUE, N.M. -- The Pit is going to be a house divided tonight.

The C-Unit is here. The Rebellion is here.

Colorado and UNLV alumni are missing work due to sudden cases of March Madness. Many of them have made the 349-mile trip from Boulder and the 483-mile trip from Las Vegas looking for a cure.

New Mexico fans will have to decide whether to root for the rival Rebels out of conference loyalty or the underdog Buffs.

No. 11 CU takes the NCAA Tournament stage for the first time in nine years tonight against No. 6 UNLV in a second-round South Regional game at the legendary Pit (tip at approximately 8 p.m., truTV).

UNLV’s Anthony Marshall reacts after a New Mexico turnover in the first half of a semifinal NCAA college basketball game during the Mountain West
UNLV's Anthony Marshall reacts after a New Mexico turnover in the first half of a semifinal NCAA college basketball game during the Mountain West Conference tournament, Friday, March 9, 2012, in Las Vegas. (AP Photo/Julie Jacobson) ( Julie Jacobson )

"I had a couple of them write me on Twitter saying they'd be here and supporting us and stuff like that," Rebels guard Anthony Marshall said of the rabid Lobos faithful. "If New Mexico had a game in Las Vegas, our fans would be out there supporting them just to keep it in the Mountain West. So hopefully they do."

The Buffs (23-11) might not need any help from the locals if they play with the same swagger and intensity they brought to the Pac-12 Tournament. CU took down Utah, Oregon, Cal and Arizona in consecutive day at the staples Center.

"It may be a bigger stage, certainly nationally," Boyle said. "But in terms of what we're here to do and how we want to approach UNLV, it's no different than how we wanted to approach Utah in the first round of the Pac-12 Tournament."

Boyle has guided the program to its first NCAA Tournament appearance since 2003 (CU lost 79-64 to Michigan State in the first round).

Chauncey Billups led the Buffs to their last victory in the Big Dance, a memorable 80-62 win over Indiana on March 14, 1997. Dean Smith passed Adolph Rupp to move into first on the all-time wins list at CU's expense in the second round as the Tar Heels won 73-56.

This is the program's third appearance in the NCAA Tournament since 1970. This is the third consecutive appearance for many of the Rebels.

"We've got work to do though on a national scale in terms of respectability," Boyle said. "We've got an opportunity (tonight) to start on that journey."

UNLV grabbed headlines from coast to coast with its upset of No. 1 North Carolina (90-80) on Nov, 26. But the Rebels had a tough time playing Front Range teams on the road this season, beating Air Force in overtime and losing to Colorado State and Wyoming.

The altitude in Albuquerque, where UNLV lost to New Mexico 65-45, is 5,314 feet. The altitude at the Coors Events Center is 5,345 feet.

"I feel like we played at elevation a lot this year. We've struggled in it and played well in it," Rebels forward Mike Moser said. "I wouldn't say that's going to be the deciding factor in this game."

Transition defense is how the Buffs plan to survive and advance. Boyle's team plans to run with the Runnin' Rebels ... carefully.

"We have to be smart," senior point guard Nate Tomlinson said. "But we're not going to hesitate. When we get a stop, we like to run, and we're not going to change our game at all. We're picking our spots when and where we want to be aggressive."

After watching film of CU's four-win-in-four-nights act in Los Angeles, first-year UNLV head coach Dave Rice is concerned about the No. 11 seed that was picked to finish tied for 10th in the Pac-12.

The Rebels' focus is on limiting Andre Roberson's offensive rebounding, Carlon Brown's drives into the paint, and Spencer Dinwiddie's timely 3-pointers and free throws.

"Certainly we've talked about the confidence factor that Colorado played four very good games in four days. So they're coming in on a roll," Rice said. "The biggest thing is they have good players. They've got guys that do things that have given us trouble all year."

The CU-UNLV winner advances to face the winner of tonight's second-round game between No. 3 Baylor and No. 14 South Dakota State.