USC quarterback Matt Barkley met Notre Dame quarterback Jimmy Clausen about five years ago when both worked with the same private position coach.
Barkley was in eighth grade at the time, Clausen already a star at Westlake Village Oaks Christian. They still occasionally work out together during the off-season with mentor Steve Clarkson.
"We're good buds," Barkley said Tuesday after USC practiced for the first time since Saturday's 30-3 victory over California.
The Trojans have an open date this week, but they already have begun preparing for their Oct. 17 game at South Bend, Ind.
Barkley has completed 59% of his passes and has thrown for three touchdowns with two interceptions in four starts.
Clausen is thriving for the Fighting Irish after more than two years of starts and stops. He leads the nation in passing efficiency, completing 68% of his attempts with 12 touchdowns and two interceptions in five games.
"I respect him as a quarterback -- I think he's awesome regardless of what people say about his attitude," Barkley said. "I like the kid.
"I think he's a great competitor, but at the same time I think he'll get a little taste of what our defense is all about next weekend."
Barkley should be at full strength by the time the Trojans play Notre Dame.
The freshman said he no longer feels pain in his right shoulder, which he injured in the Trojans' victory at Ohio State on Sept. 12.
Barkley also is buoyed by the possible return of receiver Ronald Johnson. The junior practiced Tuesday for the first time since suffering a broken collarbone in USC's final training camp scrimmage.
Johnson participated in a few passing drills but probably won't be cleared for contact until next week.
"It felt good to get out there, running and catching and playing around with the guys a little bit," Johnson said. "I feel like I'm back."
Defensive end Armond Armstead, recovering from a broken bone in his foot, performed agility drills. But the sophomore might not be cleared to practice until next week.
Longhorns in mix
While USC prepares for its second trip to the Midwest this season, school officials are working to avoid similar travel situations in the future.
Steve Lopes, a senior associate athletic director who handles scheduling, said playing nonconference opponents such as Ohio State and Notre Dame on the road in the same season was "not something you'd really like to do very often."
Lopes confirmed that he has "had conversations" with Texas and other teams from Bowl Championship Series conferences about possible home-and-home series.
USC is trying to fill dates in two-year cycles for 2015-2016, 2017-2018, 2019-2020 and 2020-2021.
USC's goal is to start series with BCS opponents at home in odd years because those are the years the Trojans travel to Notre Dame.
Defensive lineman Nick Perry sat out after he was hit on the left knee, aggravating a bruise for the second time. . . . Tailback Joe McKnight said he was sore but otherwise all right after bumping knees with a teammate during a punt-catching drill. . . . Tailback Marc Tyler (toe) jogged but said there was no timetable for his return to practice.