UC Davis (4-3) trailed most of the game while Denham, the starting quarterback, was at the helm. But Denham (20 of 35, 259 yards, TD) was forced from the game with an injury midway through the third period, with Portland State ahead 28-17.
The Aggies then caught fire behind Heyworth, the backup, who wound up 6 of 7 for 82 yards and two touchdowns. Sean Kelley's 30-yard field goal with 4:40 to play broke a 31-31 tie.
Filling in for injured starter Drew Hubel for the second consecutive week, Connor Cavanaugh finished 12 of 18 for 131 yards and two touchdowns for Portland State (2-6). He also rushed 13 times for 50 yards.