The Cardinals (4-1) used a 30-11 run to overcome a 53-34 deficit with 14:05 remaining, tying the score at 64-64 on Rakeem Buckles' basket with 4:24 left. Bellfield answered with six straight points, and the Runnin' Rebels (5-0) managed to hang on in a game they never trailed.
The Cardinals were coming off a four-game sweep in the Hall of Fame showcase, including a 96-66 rout of Arkansas. But they were unimpressive in a 69-56 win over East Tennessee State and a 90-81 victory over Morgan State, and were stung again by the Runnin' Rebels.
UNLV went into Freedom Hall and won 56-55 last season. Before that, Louisville had won four straight in the series dating to 1993.
Darris Santee added 13 points and a key block in the final minute for UNLV, which led 40-30 at halftime. Derrick Jasper added 12 points and Chace Stanback finished with nine rebounds and two blocked shots.
The Cardinals tied the score at 20-20 on Sosa's lay-up with 9:30 left, but the Rebels shot 56 percent from the field (15 of 27) over the first 20 minutes and led 38-27 following Willis' free throw with 2:24 remaining.
Bellfield scored nine points and Willis had eight during the first half.