An in-season coaching change lit a spark under an underachieving USC program two years ago. The Trojans can only hope for similar results as they enter yet another chaotic period.

Staggering from a stunning home loss and Steve Sarkisian's sudden dismissal, the Trojans begin a challenging stretch under interim coach Clay Helton with Saturday night's rivalry game at 14th-ranked Notre Dame.

Sarkisian's eventful 18-game tenure at USC (3-2) came to an abrupt end Monday, one day after the beleaguered coach was placed on leave by athletic director Pat Haden for coming to practice in an unfit state and four following the then-No. 17 Trojans' 17-12 loss to Washington as a double-digit favorite. Though Haden declined to offer specifics, the decision came less than two months after Sarkisian admitted to combining alcohol and medication before giving a speech while appearing intoxicated during a preseason pep rally.

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Helton, a holdover from Lane Kiffin's staff in his third season as offensive coordinator, takes over a Trojans team that made its last trip to South Bend, Indiana, under similar turmoil in 2013. Kiffin was fired two weeks prior to that 14-10 loss when a 62-41 defeat at Arizona State left USC 0-2 in Pac-12 play.

USC proceeded to win six of its next seven games under Ed Orgeron before losing the regular-season finale to UCLA. Helton also was interim head coach for the Trojans' 45-20 Las Vegas Bowl victory over Fresno State after Orgeron resigned upon learning he wouldn't be a candidate for the permanent job.

''A lot of these guys, fortunately or unfortunately, have been in this situation before,'' said Helton, who will continue to call plays. ''You have to be yourself, and you have to coach it your own way. I told the guys, we're going to win a lot of ballgames here and we're going to have a lot of fun."

Despite the apparent state of disarray, Fighting Irish coach Brian Kelly isn't taking the talented Trojans lightly.

''Teams come together under those circumstances and they're going to play their very best,'' Kelly said. ''It's a rivalry game for them as well. It's a chance for them to respond. You look at the way Texas responded this past weekend with a lot of media scrutiny. I expect USC to respond the same way.''

Kelly does have reason for concern. USC, ranked eighth in the preseason AP Top 25, dominated well-regarded Arizona State on the road in Sarkisian's second-to-last game and piled up 577 total yards in a 49-14 home rout of Notre Dame (5-1) last season. Though the Irish claimed the Jeweled Shillelagh the previous two meetings, the Trojans won nine of 10 in the series prior to that stretch with an average margin of victory of 23.3 points.

Cody Kessler threw for 372 yards and six touchdowns in last year's triumph but was held to 156 yards and intercepted twice against Washington. The senior had just one interception with 15 touchdown passes over the first four games.

While Kessler struggled last week, DeShone Kizer has kept Notre Dame in the College Football Playoff chase with efficient quarterback play in place of an injured Malik Zaire. The redshirt freshman is completing nearly 66 percent of his throws with eight touchdown passes while directing a balanced offense that's averaged 508.5 yards in his four starts.

Kizer has been aided by a strong running game headed by C.J. Prosise, who turned in a fourth 100-yard effort in five games by gaining 129 with three touchdowns in last week's 41-24 win over previously unbeaten Navy. Two of those scores came after the Midshipmen lost fumbles deep in Notre Dame territory that helped the Irish bounce back from their two-point loss at No. 5 Clemson on Oct. 3.

Notre Dame's 238.8 rushing yards per game ranks 13th in the FBS while USC's inconsistent defense has allowed 182 or more in three of its five contests, a reason why the Trojans are 125th nationally in time of possession (25:09).