Five things we learned in USC’s 59-9 victory over Idaho

Five things we learned in USC’s 59-9 victory over Idaho:

Cody Kessler can throw deep

After missing several open receivers against Arkansas State, quarterback Cody Kessler endured a week of criticism and second-guessing about his ability to throw accurate longer passes.

The fifth-year senior answered with three outstanding passes for touchdowns and a career-best 410 passing yards.

Kessler’s weeklong focus on improved footwork and timing resulted in a 50-yard touchdown to receiver JuJu Smith-Schuster, a 28-yard touchdown to receiver Isaac Whitney and a 41-yard scoring strike to Smith-Schuster.

Offensive coordinator Clay Helton’s play-calling and a porous Idaho defense created wide-open opportunities for Kessler and the receivers.

The next challenge for Kessler will be delivering those kinds of throws to receivers facing tight coverage.

Justin Davis is back, and perhaps better

Tailback Justin Davis, who sat out the opener because of a rib injury, returned against Idaho and ran like a player fighting for a position.

After watching senior Tre Madden recapture his 2013 form and freshmen Ronald Jones II, Aca’Cedric Ware and Dominic Davis in their debuts against Arkansas State, he might have had extra motivation.

Justin Davis showed elusiveness, speed and will on a 43-yard breakaway in the first quarter, then scored on a one-yard touchdown run. He scored again on a seven-yard run, and finished with 74 yards in five carries.

The junior’s impressive return could create a logjam at tailback.

All have played in the first two easy games, but that could change as the Trojans begin the more challenging part of their schedule, beginning Saturday against Stanford.

Madden, Davis and Jones, who rushed for a team-best 83 yards and touchdown against Idaho, will probably get those opportunities.

Third down is a concern

USC demonstrated big-play capability against overmatched opponents, but it struggled to convert third downs.

The Trojans made just three of 10 against Arkansas State and one of six against Idaho.

They could get away with that against Sun Belt Conference teams, but not the Pac-12 Conference.

Helton’s third-down play-calling and execution by Kessler and other offensive players must be better if the Trojans expect to sustain drives and win closer games.

The offensive line improved

USC’s offensive line came under scrutiny after surrendering five sacks in the first half against Arkansas State.

The line gave up no sacks against Idaho, extending its streak to six quarters.

Senior center Max Tuerk said communication along the line was vastly improved after a week of practice to correct mistakes.

The line also established running room for backs who amassed 284 rushing yards.

The pass rush needs work

USC has yet to consistently pressure the quarterback.

Arkansas State’s offense, with a dual-threat quarterback, was a challenge, but Idaho’s more traditional offensive attack invited sacks.

The Trojans got just one, increasing their season total to two.

For all the talk about improved depth in the defensive line, the Trojans are still searching for playmakers who can chase down the quarterback and force turnovers.

gary.klein@latimes.com

Twitter: @latimesklein