The first boos trickled down from the Coliseum crowd with 14:47 remaining in the second quarter.
So much for USC enjoying any sort of honeymoon at the start of this, their most promising football season in recent years.
"It didn't get to us," offensive lineman Chuma Edoga said. "You know how fans are."
The problem is, the Trojans came into their opener against Western Michigan ranked No. 4 and considered a strong contender for a spot in the College Football Playoff at season's end.
That puts them smack dab in the national spotlight, where expectations run high and perceptions can matter.
Their 49-31 comeback win on Saturday afternoon wasn't as pretty or as convincing as the scoreboard might suggest. If fans were less than thrilled, how will the CFP selection committee feel in December?
"We know there's a lot of progress to be made and very quickly," coach Clay Helton said. "I'm happy with the win but I'm also a realist that there's a lot of work to be done."
The offense suffered too many stutters and the veteran defense gave up too many yards on the ground. Special teams weren't that special.
Fans started booing with a dropped pass in the second quarter and grew louder with another. Whistles rained down when Helton chose to punt on fourth-and-four a few minutes later.
This wasn't like past seasons when the Trojans stared at No. 15 or No. 20 and could fly under the radar for a while. There was a palpable squirming when Western Michigan's Darius Phillips returned a fourth-quarter kickoff for a touchdown, his underdog team pulling even at 28-28 with less than eight minutes remaining.
"We were mashing them up," Broncos quarterback Jon Wassink said, adding, "We found out what we were made of and USC found out what they were made of, too."
The stadium thermometer was stuck past 100 degrees and the sky was hazy from fires to the north, all of which might have explained the desultory performance and the half-full stands.
The mood among USC players after the game was something less than celebratory, with concerns about missed opportunities and what quarterback Sam Darnold characterized as "dumb mistakes."
Looking ahead, if the Trojans rebound against No. 14 Stanford next week, if they stay undefeated the remainder of the regular season, Saturday will be a blip on the radar, long forgotten.
Darnold talked about "just continuing to have a one-game-at-a-time mentality. I think if we continue to have that mentality we're going to be hard to stop."
Western Michigan could also play a role.
The Broncos put together a Cinderella run last season, going 13-1 with their only loss against Wisconsin in the Cotton Bowl. They aren't expected to be as good this fall, but if they manage another winning streak, Saturday's result looks a lot better for USC.
On the flipside, the potential ramifications of a closer-than-expected score come into play if Western Michigan proves to be average or worse and the Trojans end up in a traffic jam of one-loss teams fighting for the last four spots.
Even if margin of victory doesn't factor into the equation, the CFP selection committee will compare records and strength of schedule when it begins issuing rankings in late October.
A number of the teams clustered around USC in the AP Top 25 poll, which arguably sets the tone for early discussions, scored impressive wins or dominated underdog opponents this weekend.
It might seem premature to be thinking about all this in the first days of September. USC safety Chris Hawkins preferred to put an upbeat spin on the Western Michigan game.
"I mean, [the fans] were cheering at the end of the game," he said. "That's all that matters."
But that's the tricky part about vying for a playoff spot.
Like it or not, teams such as Alabama, Ohio State and Clemson know the nation is watching their every move from the start. Small missteps can become magnified in the race for the national championship.
As good as they might be- — or become — the Trojans must live with that degree of scrutiny. As Darnold said: "It's hard to ignore."