LAS VEGAS -- San Diego State came out strong in the second half, showing why it is undefeated when leading at the break.

The eighth-ranked Aztecs used a 19-9 run to open the second half, extending their lead to 15 points en route to a 59-51 victory over UNLV in the semifinals of the Mountain West Conference tournament on Friday night.

San Diego State improved to 23-0 when leading at halftime.

"We came here to win three games," Aztecs coach Steve Fisher said. "We came here to compete like crazy. We've done that for two. We got one to go."

Dwayne Polee II came off the bench to lead the Aztecs (29-3) with 18 points and six rebounds. Xavier Thames added 17 and six assists for San Diego State, which will face New Mexico in the title game on Saturday.

The Aztecs scored 12 points off of turnovers, outrebounded UNLV 34-29, and outscored their league rivals 11-4 with second-chance points.

"I thought the difference in the game really was second chance points and then the fact that we had a few key turnovers," UNLV coach Dave Rice said. "But I was proud of the fact we kept battling, working the entire game. We didn't give up. We got down, hung in there, and got ourselves within striking distance."

The feisty Runnin' Rebels kept it close in the first half, and made a last-minute rally, but it wasn't enough against the quicker and defensively sound top-seeded Aztecs. Trailing 50-37 with just under six minutes left in the game, UNLV's Bryce Dejean-Jones scored seven points during a 14-6 run to cut the lead to five with 48.9 seconds to go.

But Polee, who fell one point short of tying his career-high, made 5 of 6 free throws down the stretch to seal the Aztecs' win.

"As the sixth man, that's what I like to do, is be the sparkplug for our team," Polee said. "Whether it's offensively or defensively, I like to come in and bring a lot of energy."

Despite shooting a bleak 36.4 percent from the field on 20 of 55 shooting, San Diego State drained 14 of 17 free throw attempts in the game.

San Diego State got 26 points from its reserves, outscoring UNLV's bench by 12.

Thames, the Mountain West player of the year, turned the ball over just one time, and through two games in the tournament, he has 13 assists with just two turnovers.

"They're a great team," Thames said. "We knew they were going to fight hard and come back. We just wanted to get on a run. We talked (about it) at halftime. I think that's what we did."

During their six-game win streak the Aztecs have knocked off No. 21 New Mexico and UNLV twice, while four of the six games have been away from home.

And while San Diego State is assuredly headed to the NCAA tournament, the loss dealt a severe blow to UNLV's chances of making it for a fifth consecutive year.

Deville Smith led the Rebels (20-13) with 17 points, while Dejean-Jones scored 10 and Khem Birch added six points, 15 rebounds and five blocked shots.

San Diego State, which has advanced to the title game five of the last six years, has now handed UNLV seven of its last 23 home losses. The Aztecs held the Rebels to their fewest points in a loss this season.