Steve Sarkisian has been generally in charge of the offensive playcalling whereever he's been as a head coach in Washington and USC. That will change a bit this season as current offensive coordinator Clay Helton will be taking over more of the playcalling. Sark will focus more on specific head coaching responsibilities, which I guess would be overall management and recruiting areas.
Helton was named the offensive coordinator for USC in 2013 when Lane Kiffin did something similar in delegating last season. Kiffin was fired and Helton stayed on with replacement coach Ed Orgeron. When Orgeron was fired, Helton became the interim head coach in their bowl game (which turned out to be a rout of Fresno State in the Las Vegas Bowl). Sarkisian retained Helton, who has held the title of offensive coordinator but generally was more responsible for quarterback coaching.
Tee Martin will go up to the press box. Helton will come down to the field and call plays on the sidelines. Sarkisian will still have some playcalling input on third downs and red zone situations, but for the most part the offense has been turned entirely over to Helton on gameday.
Tre Madden will get the start as the number one running back. Justin Davis is still questionable.