Clay Helton enters his fourth full season under more pressure than any time in his USC career following a 5-7 season.Fans are angry, and many skeptics wonder whether Helton can turn the Trojans’ fortunes around after a mistake-laden 2018 that proved USC could not sustain success without quarterback Sam Darnold. USC lost not only to traditional rivals UCLA and Notre Dame, but also to California for the first time since 2003. MORE: SN’s pre-preseason rankings for 2019Helton hired offensive coordinator Graham Harrell from North Texas as the Trojans switch to an Air Raid offense 2019. The less-is-more philosophy of Harrell’s Air Raid contains just four running plays and requires quick decisions from the quarterback — whoever that may be in 2019. Whether it suits USC remains to be seen.USC, unranked in Sporting News’ pre-preseason top 25, faces a make-or-break year in 2019. Here’s a closer look at the Trojans heading into the season:USC football schedule 2019DateOpponentLocationAug. 31Fresno StateLos AngelesSept. 7No. 21 StanfordLos AngelesSept. 14at BYUProvo, UtahSept. 20UtahLos AngelesSept. 28at No. 14 WashingtonSeattleOct. 5ByeOffOct. 12No. 8 Notre DameNotre Dame, Ind.Oct. 19ArizonaLos AngelesOct. 25at ColoradoBoulder, Colo.Nov. 2No. 13 OregonLos AngelesNov. 9at Arizona StateTempe, Ariz.Nov. 16at CalBerkeley, Calif.Nov. 23UCLALos AngelesNov. 30ByeOffDec. 6Pac-12 championshipSanta Clara, Calif.Bold denotes Pac-12 gamesMORE: Early predictions for 2019 seasonUSC football recruiting 2019The disappointing season and uncertainty around Helton contributed to the Trojans’ 20th-ranked recruiting class, good for third in the Pac-12, according to 247Sports’ Composite team rankings. That was USC’s worst class since 2001. The highest-rated recruit — after five-star receiver Bru McCoy backed out of his letter intent and transferred to Texas — is four-star receiver Kyle Ford (Orange, Calif.), but he might redshirt after tearing knee ligaments last season. Four-star defensive end Drake Jackson (Corona, Calif.), who enrolled in January, is already part of the rotation and should see plenty of playing time.USC football roster 2019USC’s football roster will be updated in the spring and fall here.MORE: 2019 Pac-12 primerWhat to watch from USC in 20191. Who starts at quarterback?Former five-star recruit JT Daniels started all but one game last season as a true freshman, but was unconvincing as he threw for 2,672 yards and 14 touchdowns to 10 interceptions. Harrell has already promised an open competition. Many players prefer sophomore Jack Sears, who started one game in 2018. Junior Matt Fink and first-year freshman Kedon Slovis have enjoyed good springs, however, so there’s not a lot of separation among the four quarterbacks.Helton favors Daniels, so Harrell would need to really like someone else for the Trojans to make a change. The two coaches will both have a say in who starts; this could be an early test of how resistant Helton is to ceding power.2. Can the secondary survive?USC is untested at cornerback with sophomore Greg Johnson and freshmen Isaac Taylor-Stuart and Olaijah Griffin. Only Johnson got a real chance last season and was demoted from the starting lineup before he got hurt. The safeties — Talanoa Hufanga and Isaiah Pola-Mao — are promising, but both were injured last season. Hufanga has already broken his collarbone twice. The Trojans bring in eight defensive backs for depth, including incoming freshman Briton Allen, who played cornerback and safety in spring drills. 3. Can USC become more disciplined?Helton is acting sterner in spring, placing a strong emphasis on reducing penalties (the Trojans were the ninth-most penalized team in 2018, averaging eight per game). Moreover, it appeared players stood up to coaches several times on the sidelines last year, painting a picture of disarray.This might be the most important issue to determine whether USC can really improve from last season. USC always has talent, but it needs to organize it properly — it can’t have 10 men on the field for special teams plays like last season. If USC fixes this issue, it could experience success in the maligned Pac-12.