Ohio State defensive coordinator Greg Schiano speaks to the media on Dec. 27 prior to the 2017 Cotton Bowl in Dallas, Texas. Credit: Jack Westerheide | Photo EditorDALLAS — In April, should he decide to forgo his final year of eligibility, USC quarterback Sam Darnold will likely be selected at the top of the first round of the 2018 NFL Draft.But before one of the top quarterbacks in the nation likely turns his attention to professional football, he first will face a formidable Ohio State defense Friday at AT&T Stadium in the Cotton Bowl.Ohio State might present the biggest test Darnold will face all season. The Buckeyes have allowed the 20th-fewest passing yards per game and seventh-fewest passing yards per attempt. This matchup also could wind up being the Buckeyes’ toughest challenge since Week 2, when they hosted the 2017 Heisman Trophy winner, Oklahoma quarterback Baker Mayfield.The Sooners’ signal-caller went 27-for-35 for 386 passing yards and three touchdowns. And if the Buckeyes are to have more success against Darnold, Ohio State defensive coordinator Greg Schiano believes the defense will need to simplify its game and not try to do too much against the Trojans.“When you’re playing an elite level quarterback or an elite level running back, and this is going to sound coach-speak, but 11 guys have to do their job,” Schiano said Wednesday. “When you look back at that Oklahoma game, some players tried to do too much and did more than their job and then what happened is when you do more than your job, you don’t end up doing your job.”The idea seems easy enough, but Ohio State senior defensive end Jalyn Holmes said keeping everything simple against talented players and teams is not always simple.Knowing the caliber of the team, players will often take an opportunity to try for a sack or make a play on the ball and open a gap in coverage, something Holmes said he has fallen victim to frequently in his career. This, he said, was particularly an issue for the team in its 31-16 loss to Oklahoma.And given the similarities between Darnold and Mayfield, there is room for concern that the defense could have another lapse and find itself on the wrong end of another blowout.Oklahoma quarterback Baker Mayfield evades Buckeye defenders in the Oklahoma- Ohio State game on Sep. 9. Credit: Jack Westerheide | Photo EditorWhile neither are considered true dual-threat quarterbacks, both have the mobility to escape the pocket and make plays outside when needed. Mayfield is more prone to designed runs, and thus has 310 rushing yards on 85 carries, 210 more yards and 21 more carries than Darnold. Both have five rushing touchdowns.Darnold is less of a threat to run, but his mobility and comfort outside of the pocket allow him to complete passes while on the move. “I think being able to kind of play and move off of my instincts has really been one of my strengths in terms of playing quarterback,” Darnold said. “I think, obviously, there’s a lot to learn from when you look at sometimes how my feet can get out of whack a little bit and I can be throwing a little sideways. But I think throwing on the run is one of my really good strengths.”Sophomore defensive end Nick Bosa said while both are elusive, Mayfield chooses to do it more out of comfort whereas Darnold will stay in the pocket if possible. That comfort in the pocket and ability to do damage with his arm without having to move is what helps Darnold separate himself from Mayfield — and is why he is considered the better NFL prospect. “Some of the throws he makes are just kind of ridiculous,” Bosa said. “Across the field, how fast he throws the ball, you can see why people are impressed with him.”In order to stop Darnold from tearing the Buckeyes apart through the air like Mayfield did, Ohio State will have to swiftly break through the Trojans’ offensive line while also containing Darnold.USC’s line will often move side-to-side to try and provide challenges for opposing defensive lines, Bosa said. Buthe said the defense has been preparing for that, and added the Buckeyes should still be able to find the holes and get to Darnold.“Just staying in your rush lane, even if a slide comes to you and you want to take that inside move or whatever it is, just staying disciplined to where you’re rushing and sometimes sacks will fall right into you if you just stay where you’re supposed to be,” Bosa said. Both Bosa and Darnold expressed excitement in the looming matchup. With a defensive line Darnold said is entirely comprised of future NFL players and a quarterback who will likely hear his name called early in the upcoming draft, both sides are eager for the chance to prove one is better than the other.Bosa, in particular, is excited for the first chance to break the line of scrimmage.“You always want to hit a high-drafted quarterback,” he said.