SAN DIEGO —Elijah Mitrou-Long scored 19 points, including two free throws with 11.5 seconds left, and U.N.L.V. handed No. 4 San Diego State its first loss of the season, a 66-63 defeat on Saturday, ending the Aztecs’ 26-game winning streak.
San Diego State, which had been the only remaining undefeated men’s team, erased most of a 14-point deficit when it pulled to within 64-63 on Malachi Flynn’s 3-pointer with less than 20 seconds left. Mitrou-Long was fouled by Matt Mitchell with 11.5 seconds left and made both free throws.
Flynn missed a contested 3-pointer with 3.3 seconds left and the ball went to the Runnin’ Rebels (15-14, 10-6 Mountain West Conference). After a long pass down the court, Mitchell ended up with the ball and his desperation shot at the buzzer fell short.
San Diego State (26-1, 15-1) unveiled a banner for winning the regular-season conference championship before the game and then looked nothing like the team that raced to the best start in program history. The Aztecs trailed by 14 midway through the second half and were down 11 with 4:32 remaining.
They were uncharacteristically porous on defense and sloppy on offense, missing easy shots and committing careless turnovers.
San Diego State had been projected as the No. 1 seed in the East Region in the N.C.A.A. tournament by ESPN’s Joe Lunardi. Providing the Aztecs do not falter again, the loss could keep the Aztecs in the West as the No. 2 seed. Gonzaga is the projected No. 1 seed in the West, where the regionals will be at Staples Center in Los Angeles.
The Aztecs will drop from their No. 4 spot in the Top 25, which matched the highest ranking in school history. The Top 25 was also shaken by No. 3 Kansas’ 64-61 win over No. 1 Baylor.
U.N.L.V.’s Amauri Hardy scored 17 points, and Bryce Hamilton added 11 points and 10 rebounds.
Flynn scored 24 points, Mitchell had 13 and Jordan Schakel had 10 for San Diego State.
The Aztecs pulled within 62-60 on Flynn’s two free throws with 1:47 left and Arop Aguek’s layup with 25.6 seconds left. Mitrou-Long then made two free throws with 19.9 seconds left for a four-point lead.
Hardy’s jumper gave U.N.L.V. a 44-30 lead three minutes into the second half before San Diego State pulled within seven. But Hardy then made a free throw and a layup to put the Runnin’ Rebels back up by double digits.
U.N.L.V. took advantage of numerous breakdowns by the Aztecs to take a double-digit lead midway through the first half and were up 37-25 at halftime after a steal and dunk by Mitrou-Long.
San Diego State never led after going up 14-13 on a Flynn 3-pointer, and then allowing U.N.L.V. to go on a 10-0 run. Mitrou-Long started it by converting a 4-point play when he hit a 3-pointer and was fouled by Flynn.
The Aztecs’ only points in a four-minute span were two free throws apiece by Mitchell and Flynn. U.N.L.V. kept connecting, though, getting a bank shot by Hamilton and a 3-pointer by Mitrou-Long to take its first double-digit lead, 28-18 with 7:12 before halftime.
San Diego next hosts Colorado State on Tuesday.U.N.L.V. will play Boise State in its home finale on Wednesday.