The vandalizing ends now for Trojans after 59-9 rout of Idaho

So much for the exhibition season.

USC’s 59-9 rout of Idaho on Saturday night at the Coliseum ended the Trojans’ two-game stint as an honorary member of the Sun Belt Conference, which amounted to nothing more than a warmup for the real part of their schedule.

USC, ranked eighth in the Associated Press media poll and 10th in the coaches’ poll, improved to 2-0 heading into next week’s Pac-12 Conference opener against Stanford.

Quarterback Cody Kessler passed for a career-best 410 yards and had three touchdown throws, all perfect strikes, as the Trojans rolled up 738 yards against another undermanned opponent.

“We’ve got plenty of stuff to clean up,” Coach Steve Sarkisian said.

After routing Sun Belt opponents by a combined score of 114-15, and paying more than $2 million for the privilege, USC plays what appear to be legitimate opponents the rest of the way.

USC maintained its status — along with UCLA and Notre Dame — of never playing a Football Championship Subdivision opponent.

But it came close against Arkansas State, which tested Missouri on Saturday, and Idaho in games that amounted to glorified scrimmages.

The games served as valuable opportunities for Sarkisian and his staff to evaluate new players. The Trojans played 23 new players against Arkansas State and they got more experience against the Vandals.

On Saturday, the Trojans also corrected some areas that were exposed as potential problems in the opener.

Kessler, who overthrew receivers several times against Arkansas State, worked all week on his footwork and timing to improve his accuracy.

It apparently paid off. He hit JuJu Smith-Schuster in stride on a 50-yard touchdown pass to put USC ahead, 21-0, in the first quarter.

Kessler, who usually operates in the shotgun formation, took the snap under center, faked a handoff to Tre Madden and lofted the ball 45 yards to Smith-Schuster. He also connected with receiver Isaac Whitney for a 28-yard touchdown and with Smith-Schuster for a 41-yard score in the third quarter.

“Our biggest thing this week in practice was that we’ve hit those plays a million times and he knew I was going to hit ‘em,” Kessler said of connecting with Smith-Schuster. “Practice makes perfect.”

Kessler completed 26 of 31 passes, with no interceptions, before giving way to Max Browne in the fourth quarter.

Smith-Schuster had been frustrated at times by double coverage against Arkansas State but he had no problems against Idaho. He finished with 10 receptions for 192 yards, both career bests.

Tailbacks Madden and Justin Davis, who returned from a rib injury, each ran for two touchdowns as the Trojans rushed for 285 yards. Freshmen Ronald Jones II (team-best 83 yards rushing and a touchdown), Aca’Cedric Ware and Dominic Davis also played well after impressive debuts in the opener.

Now the challenge might be finding opportunities to play them all.

USC’s offensive line also redeemed itself. After being sacked five times in the opener, Kessler stayed upright and had plenty of time to pick out receivers, and tailbacks found gaping holes.

“We worked really hard during the week firming up our pass [protection] and assignments,” said center Max Tuerk. “It definitely showed.”

But USC, which was three for 10 on third-down conversions against Arkansas State, was only one for six against the Vandals. Of course, the Trojans were scoring mostly at will and did not have many opportunities.

That may not bode well when they play better opponents and must sustain clock-eating drives or convert make-or-break third downs.

“We’re going to need it next week against a team that likes to hold onto the ball,” Sarkisian said.

Linebacker Anthony Sarao led a defense that played aggressively but did not force a turnover while giving up 311 yards. The Trojans recorded one sack.

So is USC ready for Pac-12 play? That’s unclear. The Trojans have not been tested, something Stanford annually provides. USC won the last two games between the teams on last-second field goals.

The Trojans’ first two games this season were decided well before halftime.

Next week at the Coliseum the real season begins.

gary.klein@latimes.com

Twitter: @latimesklein