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SAN DIEGO -- USC's Holiday Bowl showdown with Iowa on Friday is in many ways a contest of contrasting traits and clashing strengths.

Start with the head coaches. Clay Helton has been on a perennial hot seat with the Trojans, while the Hawkeyes' Kirk Ferentz is college football's model of stability as the longest-tenured active coach in the FBS.

Look at the teams' defining traits. USC is aggressive, at times undisciplined and heavily penalized, while Iowa is methodical, has built an identity around its discipline/consistency and is one of the least penalized teams in the country.

And, of course, consider the stats. One side relies on its high-flying offense to offset its inconsistent defense, while the other bleeds the clock offensively to support one of the stingiest defenses in the country.

That final point is the most intriguing factor about this matchup Friday evening -- and more specifically, the compelling storyline is pitting a USC passing attack that ranks sixth nationally (335.9 yards per game) vs. an Iowa pass defense that ranks 11th (giving up just 184.2 YPG through the air).

And yet, in scouting the Hawkeyes these last few weeks, Trojans offensive coordinator Graham Harrell says what stands out most to him is actually an overriding similarity between the units.

"I think they do a lot of things well. Most importantly, they all know what they're supposed to do, they're disciplined in what they're supposed to do and they kind of execute their defense at a high level," Harrell said. "Philosophically, they probably are similar to us -- we're going to do what we do, we're going to execute it well. So it will be a good test."

Impressively, Iowa (9-3) held seven of its 12 opponents this season to fewer than 150 passing yards -- Rutgers (47), Middle Tennessee State (136), Michigan (147), Penn State (117), Northwestern (138), Illinois (144) and Nebraska (100).

That said, the Hawkeyes were not unbeatable through the air as Minnesota passed for 368 against them and Iowa State and Purdue threw for 327 each.

Asked if he saw any similarity between Iowa's defense and another his Trojans have faced this year, Helton said Cal would be the closest match with its aggressive safeties and quarters coverage looks. QB Kedon Slovis lit up Cal for 406 yards, 4 touchdowns and 0 interceptions, for what it's worth, but it's hardly a true comparison as the Golden Bears rank 108th nationally against the pass (262.4 YPG allowed).

Iowa should indeed be the toughest defense USC has faced all season. In addition to the aforementioned stifling pass defense, the Hawkeyes allow only 120.1 rushing yards per game (24th nationally) and altogether have the fifth-best scoring defense at just 13.2 points per game allowed.

"It's one of the best defensive fronts that we've faced all year," Helton said. "I think they do a great job on first and second-down efficiency. They're so well coached -- you don't see them missing assignments or getting out of gaps, and if they get you in third-and-long, they're elite. I truly believe their pass rush on third down allows them to play advantage coverages because they can rush four and get to you. That's always a deterrent for offenses -- you have to stay in that third-and-manageable against them."

To Helton's points, Iowa has a projected first-round NFL draft prospect in defensive end A.J. Epenesa (29 tackles for loss and 19.5 sacks over the last two seasons), who is essential to the Hawkeyes' 4-2-5 scheme. When working in on concert, that pass rush and the amble defenders left in coverage work to disrupt a passing attack on both ends of the operation. (Cornerback Michael Ojemudia leads that secondary with 3 interceptions and 7 passes defensed.)

While Harrell noted that many defenses this season have come up with fresh wrinkles against the Trojans, reiterating his earlier point he thinks he knows what to expect from the Hawkeyes. He actually coached against Iowa and defensive coordinator Phil Parker when he was at North Texas, and he said he sees the same general approach on film with this 2019 defense.

"What they've shown on film, it's the same over and over. What they've shown on film is a ton of four down [linemen] and a lot of teams haven't done that," Harrell said. "Sometimes we go out there and they do things different than what you see on tape so we'll be prepared for whatever, but as far as just lining up and playing what they play they're probably a little different than anyone we've played from that standpoint. … I'll be interested to kind of see early on what their plan is against us, but I would assume it's just do what they do."

Which means, he emphasized, it will simply be about which side executes what it does the best.

"Again, when we play well and we do things right, I think we can move the ball on anyone, and so we need to go play well," he said.

While this may be a different -- and tougher -- challenge than USC's offense has faced all season, it goes both ways.

The Trojans' offense with its deep stable of very good to elite wide receivers and Slovis, about whom Ferentz has raved about this week, presents the same new obstacle to Iowa.

Two of those aformentioned teams who did have success through the air against the Hawkeyes rank among the top passing offenses nationally -- Iowa State (8th) and Purdue (12th) -- like the Trojans. But, Ferentz made clear, the stats don't tell the whole story.

"Totally different," he said of preparing for the USC offense. "I flashback to our first bowl game against Texas Tech [in the 2001 Alamo Bowl]. The roots of that whole system started then with coach [Mike] Leach so it's going to be a big, big challenge for us. It's a tough preparation and it's going to be tough to play them out on the field because they've got really outstanding players.

"Their receiver corps is as good as we've seen. And [QB Kedon Slovis] is extremely impressive for any age, but for a freshman it's uncanny how poised he is back there and he's slippery. So it's going to be a challenge for us."

Slovis comes into the game completing 71.8 percent of his passes for 3,242 yards, 28 touchdowns and 9 interceptions, while spreading it around to Biletnikoff Award finalist Michael Pittman (95 catches for 1,222 yards and 11 TDs), Amon-Ra St. Brown (68-879-6), Tyler Vaughns (68-858-6) and emerging freshman Drake London (35-533-4).

Taking just the stats after Slovis returned after missing most of two games with a concussion, USC averaged 367.1 passing yards over its final seven games -- which would rank third nationally overall if it were the full-season average. Over the last five games as the offense really seemed to fully settle into this new scheme and its young, developing QB, the Trojans averaged 413.6 passing yards per game -- only Leach's Washington State team averaged more for the full season (444.3).

Factoring in the pass protection as a pivotal variable to the whole operation, the matchup between that USC passing offense vs. Iowa's defense is the one that will likely dictate the outcome of this game -- and one that should make this Holiday Bowl pairing pretty intriguing for college football fans.

Even if the players aren't quite building it up in that way.

"I guess it's a good matchup from a fan's point of view. It's everything you want to see -- good defense vs. a good offense," Slovis said. "But there's so many other factors in the game. For us, we just focus on going out and executing. We've talked about it all year and nothing really changes this week."

That's the hope, at least.

On the other side of the matchup, Iowa comes into the game ranked 98th in total offense (369.8 yards per game) and 99th in scoring (23.8 points per game).

Senior quarterback Nate Stanley has completed 58.9 percent of his passes for 2,738 yards, 14 TDs and 7 INTs. The backfield has been divided between Mekhi Sargent (117 carries for 543 yards and 4 TDs), Tyler Goodson (116-590-4) and, more so earlier in the season, Toren Young (77-414-1). And Ihmir Smith-Marsette leads a balanced receiving coreps with 42 catches for 676 yards and 4 TDs.

Here's what USC's coaches said about the matchup with the Hawkeyes' offense:

Helton: "[They're going to come out in] 12 personnel, 22 personnel, 21 personnel -- a team that loves to be first-down efficient and try to get to third-and-1-3. They remind me of the old Stanford teams, they really do, the old Stanford days of that where they're going to run the play clock all the way down. So this is another great opportunity for our defense, and we've talked about how important it is to be able to match personnel, to be able to get the communication correct, the gap-integrity correct and bring the physicality. This is one of the better run teams in the country and they really play to their defense -- they hold on to the ball with long drives and do a great job of being able to take all the play clock down and only giving up like 64 plays a game to the opponent."

Defensive coordinator Clancy Pendergast: "They present a lot of problems with their different personnel groups they use -- a very different style offense than we faced throughout the year on a consistent basis. ... They use one fullback, they use two tight ends, use three tight ends, they'll use three wide receivers. Just multiple in terms of the different looks that they give."