LOS ANGELES -- Dropped passes, missed tackles and turnovers threatened to spoil the highly anticipated season-opener for No. 4-ranked USC, but the Trojans rallied for a 49-31, come-from-behind win over Western Michigan on Saturday at Los Angeles Memorial Coliseum.

USC slammed the door on upset-minded Western Michigan with a 52-yard touchdown run from running back Stephen Carr with 3:49 left, followed 36 seconds later by a 37-yard interception return for a touchdown by safety Marvell Tell to cap the scoring.

The Trojans took the lead for good late in the fourth quarter when a 42-yard toss from quarterback Sam Darnold to wide receiver Deontay Burnett helped set up running back Ronald Jones II's third rushing touchdown of the afternoon, a 37-yarder.

"I feel stronger after gaining weight this offseason," Jones said, while also spotlighting the blockers. "The offensive line and receivers did a great job of freeing the run. They made (the ball-carriers') jobs easier."

The USC offense came alive in the fourth quarter, scoring as many points in the final 15 minutes -- 21, plus another seven on Tell's interception return -- as it did in the first three quarters combined.

"I love the poise the offense showed coming down the stretch," USC head coach Clay Helton said. "Between the runners and the offensive line, I thought they won us the football game."

Trailing 35-28, Western Michigan threatened once it regained possession, reaching the red zone on a 48-yard rush by running back LeVante Bellamy that nearly ended in a fumble. USC cornerback Iman Marshall chased Bellamy down to knock the ball loose, but video review overturned the initial call, giving the Broncos one last gasp, but they came away with only three points on a 43-yard Josh Grant field goal that cut the Broncos' deficit to four points.

USC had gained its first lead since the game's opening drive with just 8:07 remaining in the game when Carr scored on a 1-yard touchdown rush that put the Trojans ahead 28-21. Thirteen seconds later, Western Michigan's Darrius Phillips returned the kickoff 100 yards to create the fourth tie of the game.

"I didn't get many (opportunities for) kick returns, punt returns throughout the game, so when we got this one, we knew we just had to go and get it," Phillips said.

After a first-possession touchdown from Jones, Western Michigan controlled the first half with a multifaceted run game -- backs Bellamy, Jamauri Bogan and Jarvion Franklin combined for 132 yards by intermission, with quarterback Jon Wassink adding another 29 -- and an aggressive pass rush on defense.

The Broncos sacked preseason Heisman Trophy candidate Darnold three times. He was sacked just six times in his 10 starts of the 2016 season.

Under that duress, Darnold finished with 289 yards passing and went without a passing score for the first time in 11 games as USC's starter. He completed 23 of 33 passes with two interceptions.

"We knew the country would expect us to fold...Ran out of gas a little bit at the end, but really proud of the way our guys played," Bogan said. "USC, at the end of the game, shook our hands; they felt us."

Indeed, Helton said Western Michigan came at the Trojans with the tenacity of a team "that won 13 games last year."

The Broncos finished the 2016 campaign ranked in the Top 20 and played in the Cotton Bowl at the culmination of a perfect regular season.

Western Michigan held leads of 14-7 in the second quarter and 21-14 in the third, the latter secured on Wassink's 27-yard touchdown reception via a double-pass from fullback Keishawn Watson.

An interception by defensive back Sam Beal made over USC wide receiver Jalen Greene on the ensuing possession brought the Coliseum audience of 61,125 to a hush. On his next opportunity, however, Darnold capped an 83-yard drive with a 11-yard touchdown rush off a bootleg, his lone score of the day.

NOTES: Blind USC long-snapper Jake Olson made the snap on USC's final extra-point attempt. ... Darrius Phillips' kickoff return for a touchdown was the fourth of his career, and third of 100 yards or more. ... Saturday marked USC RB Ronald Jones II's eighth consecutive game with at least one rushing touchdown, and the second with three or more in his career. ... USC LB Cameron Smith missed the first half, serving a one-half suspension due to a targeting penalty in January's Rose Bowl. ... Before Saturday, neither USC nor Western Michigan had faced a current member of the other's conference, the Pac-12 and the Mid-American.