Kekoa Sasaoka missed a 23-yard field goal attempt for Southern Utah (1-4, 0-1) with 2:10 remaining.
Hamler had scoring runs from 6 and 13 yards in the second quarter and finished with 65 yards rushing on 20 carries. Jeffrey's 4-yard TD run stretched the Mustangs' lead to 24-13 with 12:47 to play.
The Thunderbirds answered less than a minute later when Chris Helbig threw a 56-yard touchdown pass to John Mitchell to pull Southern Utah to 24-21. Cal Poly had a turnover and punted on its last two possessions. Helbig then led a 10-play, 51-yard drive that stalled on Sasaoka's missed field goal.
Helbig finished 19-of-34 passing for 246 yards and two touchdowns. Jay Green ran for a 20-yard touchdown late in the third quarter.
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