Pumphrey scored three of his touchdowns in the second quarter as the Aztecs (2-2, 1-0) surged ahead to lead 28-10 at halftime. He also broke away on a 71-yard score on San Diego State's second drive in the first quarter.
Quinn Kaehler finished with 209 yards on 16-of-27 passing and Larry Clark had 71 yards on 4 receptions for the Aztecs. Donny Hageman kicked field goals of 24 and 31 yards to cap two time-consuming drives in the fourth quarter.
Blake Decker threw for 346 yards with a touchdown and two interceptions for UNLV (1-4, 0-1). His 2-yard rushing score made it 31-17 with 10:47 remaining, but the Rebels couldn't pull any closer.