Williams' punt return in the first quarter sparked Boise State, while the Broncos' defense stymied Troy all game long to post a 24-13 victory on Saturday in the season opener for both teams.
"I saw the ball for the first two seconds and then I couldn't see it anymore," said Williams, who shaded his eyes during the kick. "I just trusted my training and the ball came right to me."
Williams, who walked on last season and earned a scholarship during fall camp, did the rest. He broke two tackles and stiff-armed a defender to the ground before racing untouched the rest of the way. Williams finished with 172 kick return yards.
"Avery has that fearless mentality to go back there and be a punt returner," Boise State coach Bryan Harsin said. "I did not know about his return ability when spring camp started. We just knew that he could catch almost every punt."
With the victory, the Broncos avoided their first loss in a home-opener since falling to Washington State 41-20 in 2001.
Boise State's offense sputtered most of the afternoon, but it didn't matter much due to the Broncos' smothering defense.
Troy mustered only 215 yards, matching the Trojans' lowest offensive output since a 66-0 loss to Georgia in 2014. The Trojans' only touchdown came on a 53-yard interception return by Blace Brown.
Despite Boise State's stout defense, the game was still Troy's for the taking. However, the game turned on a bizarre play with the Trojans trailing 17-10 and driving for a tying score late in the third quarter.
Troy quarterback Brandon Silvers' pass was almost intercepted by Reid Harrison-Ducros when he stepped in front of receiver Deondre Douglas and appeared headed for a possible pick six.
However, Harrison-Ducros juggled the ball and slipped, allowing Douglas to snatch the ball out of the air at the Boise State 10 and sprint back toward the end zone. But Boise State's Desmond Williams dove toward Douglas, dislodging the ball at the 1 before it went out of the back of the end zone, resulting in a touchback.
The play was initially ruled a touchdown, but was overturned after a brief review. Troy's offense never recovered.
"That's not just one play, but that's an identity that you're creating," Harsin said of Desmond Williams' hustle to knock the ball out of Douglas' hands. "We want guys doing that on every single play."
With the departure of NFL draft pick Jeremy McNichols, sophomore Alexander Mattison picked up the slack in the Boise State ground game, rushing for 82 yards on 13 carries, including a career-long run of 49 yards for a touchdown.