San Diego State completely shut down Zach Wilson and BYU's offense last season in a 13-3 home victory.
While I highly doubt the Aztecs hold the Cougars to three points this time, I do expect a low-scoring game with BYU struggling to solve San Diego State's defense again. 
The Cougars were held 17 points in losing to Coastal Carolina this past Saturday. San Diego State has better defensive numbers than Coastal Carolina ranking eighth in scoring defense giving up 16.3 points and third in total defense holding foes to 269.1 yards. The Under is 9-1-1 in the Aztecs' last 11 road games. 
Wilson draws a lot of media attention, but BYU has a strong defense allowing just 14.7 points per game. Only three teams give up fewer points per game. The Cougars are seventh in total defense allowing 299.9 yards per contest. The Aztecs are very weak offensively especially their passing attack, which ranks 119th. 
San Diego State's game plan is to keep the clocking moving by running the ball and playing for field position trying to make sure BYU has long stretches to go.