Joey DeMartino rushed for 120 yards to help the Aggies (3-2, 2-0 Mountain West) win their 12th straight in conference play, an ongoing school record, and their eighth consecutive road conference contest.
San Jose State senior cornerback Bene Benwikere was injured making a tackle on D.J. Tialavea midway through the third quarter. Benwikere arrived at the same time as Spartans linebacker Christian Tago, who apparently struck his teammate in the head or neck while also trying to tackle the 6-foot-4, 260-pound tight end.
Benwikere's helmet flew off, and he lay motionless for several minutes while medical staff attended to him. He was secured to a stretcher, a brace was placed on his neck and he was taken off the field on a cart. He weakly waved as he was leaving the field.
Benwikere entered the game ranked third nationally in passes defended.
Benwikere has feeling in and was moving all of his extremities. He was taken to a local hospital for precautionary measures.
Tialavea, Keega Anderson and Brand Swindall caught touchdowns pass as Utah State beat the Spartans for the fifth straight time.
Austin Lopez kicked a pair of field goals, extending his streak of consecutive field goals to 23, before missing from 42 yards out at the end of the first half, the sophomore's first career miss.
The Aggies led 23-6 at halftime.
Keeton, who leads the Mountain West in passing efficiency, threw for 260 yards on 29 of 42 passes, with no interceptions.
Utah State turned a fumble and interception into third-quarter touchdowns to take control of the game.
The Spartans took the second half kickoff and drove to the 1. On a third-and-goal, the snap sailed over Fales' head and the ball was recovered by Utah State's Zach Vigil.
That led to an 11-play, 75-yard drive, with Keeton and Swindall connecting on a 17-yard scoring play that gave the Aggies a 30-6 advantage.
Nevin Lawson intercepted Fales' pass late in the third quarter that led to Keeton's 9-yard scoring run.
Utah State had three interceptions in the game.
San Jose State linebacker Keith Smith, who leads the nation in tackles per game, had 20 tackles, 10 solo.
Information from The Associated Press was used in this report.