LOS ANGELES (AP) Southern California opened training camp Thursday under its third different head coach in seven seasons.

The Trojans now need to choose a starting quarterback and replace their entire defensive front before facing defending national champion Alabama on Sept. 3, the opening game of a schedule regarded as the most difficult in college football this season.

For a beaming Clay Helton, entering his first full season as coach after an improbable rise to the top spot at USC, he wouldn't have it any other way.

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''For a football coach this is like Christmas, and the last three days I've felt like an 8-year old at the top of the stairs waiting to go down and open his presents,'' Helton said. ''To be back out here with guys you love and some newcomers, it is a very exciting time for us.''

USC hopes Helton can bring the stability and consistency that has been lacking ever since Pete Carroll departed for the NFL's Seattle Seahawks in 2010. Getting through August without making any headlines off the field would be a good start after notable incidents in each of the last two years.

In 2014, cornerback Josh Shaw fabricated a story about how he sprained both ankles in a fall, leading to a 10-game suspension. In 2015, former coach Steve Sarkisian apologized for his behavior and profane language during a team event. Sarkisian was fired in October, and Helton went 5-2 as interim coach and led the Trojans to the Pac-12 South title.

Helton has made it a priority to get the focus back on football, even going so far as eliminating the hip-hop and rock music that used to serve as the soundtrack to practice.

''It's definitely been a little chaotic at times since I have been here,'' quarterback Max Browne said. ''Being able to stay focused, all about ball has kind of been the motto and we need to keep it that way.''

For Browne and redshirt freshman Sam Darnold, the focus is on replacing Cody Kessler. Darnold surprisingly kept pace in the competition during spring practices, with his mobility offering a different dimension to the strong-armed redshirt junior Browne's skill set. Helton plans to name a starter two weeks before facing the Crimson Tide.

''Just like it was in the spring, both are playing at a very high level, and that's what usually happens when you compete,'' Helton said.

On defense, Clancy Pendergast returns to USC after a largely successful one-year stint as coordinator in 2013. Implementing his modified 3-4 scheme will be a challenge, however, after losing all but one starter on the line and at linebacker from last season.

Cameron Smith, who does return at inside linebacker after an impressive freshman season, is recovering from a season-ending knee injury. Helton said Smith and offensive lineman Toa Lobendahn (knee) would be brought along slowly during camp, but should be ready for the opener.

There is plenty of promising talent on hand, notably rush end Porter Gustin who had 5 1/2 sacks as a freshman, but facing the punishing rushing offenses of Alabama, Stanford and Utah in the first month of the season increase the urgency for a young front.

''They are playing a lot faster, a lot cleaner,'' Helton said. ''I didn't see a lot of assignment busts to be honest with you and that makes a head coach happy to see those guys progressing so fast.''

Helton said the improved depth across the roster was also noticeable. The Trojans expect to enter the season with 82 scholarship players, its highest total following NCAA sanctions in the Reggie Bush case. That total will include defensive tackle Stevie Tu'ikolovatu, a graduate transfer from Utah joining the team as a blueshirt, or unrecruited player who can receive a scholarship after the first day of camp.

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AP college football site: http://collegefootball.ap.org