If defense wins championships, then No. 20 USC will need to have a standout defensive performance in what will be a championship-like atmosphere for their season-opening matchup against the No. 1 Alabama Crimson Tide this Saturday.John McGillen | Daily TrojanSophomore sensation · Linebacker Cameron Smith burst onto the scene as a freshman and will carry big responsbilities in his second year.Entering the offseason, the state of the USC defensive line was the most evident issue the team faced in preparing for the upcoming season. The Trojans lost five active members of their defensive line rotation from 2015 over the summer. Additionally, junior defensive lineman Kenny Bigelow — who was set to be USC’s lone upperclassmen up front this season — tore his ACL during spring workouts.To alleviate the losses on the defensive front, USC acquired former Utah defensive lineman Stevie Tu’ikolovatu via transfer. At 6-foot-1, 320-pounds, Tu’ikolovatu is a stout nose tackle who can occupy blockers and shut running lanes for the opposing offensive backs. USC defensive coordinator Clancy Pendergast’s aggressive 5-2 scheme directly asks for this type of personnel at nose tackle; Tu’ikolovatu is a perfect addition in the trenches for the Trojans. The team also added Juco transfer Josh Fatu from Long Beach Community College and retains players such as sophomores Rasheem Green and Noah Jefferson, who both had rotational roles as true freshmen last season. Redshirt junior Kahliel Rodgers has also made a transition from the offensive to the defensive line in 2016, further bolstering the depth of the USC front.Despite the additions, this will still be a relatively brand-new unit personnel-wise. The Trojans won’t have much time to shuffle out growing pains as a defensive line, either, as they are being pitted against an Alabama offensive line that has built a reputation for pushing its running backs to Heisman podiums: Just last year, Alabama’s Derrick Henry — who won the Heisman Trophy — rushed for 2,219 yards and 28 touchdowns behind the Crimson Tide offensive line.While Alabama did lose three players from its offensive front over the offseason, including Rimington Award-winner Ryan Kelly, USC’s newly formed defensive front still has an almost-immediate reality check awaiting them this Saturday.The Trojan linebacking corps’ ability to play off of whatever penetration the defensive line can provide will be pivotal against the Tide. The linebackers will be responsible for diagnosing a new-look Alabama offense, which will be spearheaded in the backfield by sophomore running back Bo Scarbrough and a new quarterback — yet to be named by Crimson Tide head coach Nick Saban.In Pendergast’s 5-2 scheme, it is primarily up to linebackers to establish the aggressive and anticipative tempo of play defensively. Similar to the 3-4 defense, Pendergast’s defense utilizes a pair of both inside and outside linebackers. In the middle, sophomore Cameron Smith assumes the main leadership role of this Trojan defense as an inside linebacker. A true freshman in 2015, Smith was a Freshman All-American and was named the Pac-12 Defensive Freshman of the Year.On the outside, many expect sophomore Porter Gustin to have a breakout 2016 campaign. A hybrid defensive end and outside linebacker, Gustin has the ability and size (6-foot-5, 260 pounds) to impact games as an edge-rusher. Joining Smith and Gustin as starters for the linebacking corps will be senior Michael Hutchings and junior Uchenna Nwosu.These linebackers have the opportunity to wreak havoc defensively and disrupt whomever it may be that will line up under center for the Tide Saturday.Alabama brings a talented wide receiver group to AT&T Stadium, primarily led by sophomore wideout Calvin Ridley. Ridley caught 89 passes for a total of 1045 yards and seven touchdowns as a true freshman in 2015.Fortunately for the Trojans, they may bear their most talent on the defensive side on the edges at the starting cornerback slots. On one side of the field, sophomore cornerback Iman Marshall is coming off of a 2015 season in which he garnered freshman All-American honors. Directly across the field from Marshall is junior cornerback Adoree’ Jackson. Jackson — who has been a Swiss army knife offensively, defensively and on special teams for the Trojans since arriving in 2014 — has made it known that his priorities will be set on performing as a defensive back this season. Entering this season, Jackson was selected to the preseason watch list for the Jim Thorpe award, which is awarded annually to the nation’s top cornerback.In the secondary for the Trojans, redshirt junior Chris Hawkins and sophomore Marvell Tell will be starting at safety and free safety, respectively. Both Hawkins and Tell have dealt with hamstring issues this fall camp, but look to be 100 percent entering the regular season.USC and Alabama are similar in that both programs are entering transitional years at the quarterback position. Whichever defense proves able to disrupt the others’ opening day, first-time starter very well may come away with the season-opening victory.