ATLANTA — Ohio State coach Ryan Day is known as an offensive whiz, able to diagnose and exploit matchups while dialing up plays for Buckeyes’ teams that never lack scoring firepower.

But now Day, just like his Ohio State program, faces one of the most complete challenges it has seen in recent years in the form of No. 1-ranked Georgia in the CFP Peach Bowl Semifinal at 8 p.m. on Saturday

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Kirby Smart, of course, is every bit the defensive coaching mastermind that Day represents on offense.

Smart won four national titles as Nick Saban’s defensive coordinator before building the most dominant defense in recent history last year, a group featuring an NFL five first-round draft picks.

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The Bulldogs’ defensive staff, with the celebrated Will Muschamp and Smart’s long-time understudy Glenn Schumann acting as co-defensive coordinators, is regarded as the best in the nation.

Georgia rarely beats itself on defense, seemingly always with ample talent and depth operating within sound, well-coached schemes that seldom “bust.”

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Day revealed during Friday’s press conference that Smart’s defense is what concerns him most in this titanic matchup of traditional

“Georgia’s defense is complete,” Day said during the coaches’ press conference at the Westin Peachtree Plaza Hotel.

“They have really good players in the back end, very, very talented, highly recruited, and been developed at a high level with a tremendous scheme.”

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Day knows his highly recruited quarterback and receivers are going to have to make plays against that star-studded secondary.

And things don’t get any easier on the front end.

“Then when you go into the front, athletic linebackers who can run sideline to sideline and their front is powerful,” Day said.

“So you see the statistics. You see the way they played all year. So they’re a complete defense.”

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To Day’s point, the Bulldogs rank among the most elite defenses in the nation in most all categories:

No. 2 Scoring Defense (12.77 points per game)

No. 1 Rushing Defense (77.0 yards per game)

No. 2 Third-Down Defense (26.7 percent)

No. 1 Red Zone Defense (60.7 percent)

No. 10 Pass Efficiency Defense (111.93)

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Day is no stranger to facing elite competition at this stage of the season, as this marks the Buckeyes third CFP trip in the past four years.

“When you get to this level of the CFP, that’s what you’re going to get, and that’s the biggest challenge,” Day said. “. So we have to execute at a high level.”