As the buzz built for tonight's matchup between No. 5 Florida State and No. 3 Clemson, the hype focused on two elite quarterbacks — FSU's Jameis Winston and the Tigers' Tajh Boyd.When the game kicks off in Clemson's rowdy Memorial Stadium, the key to what USA Today calls the biggest game in ACC history likely will rest on the other side of the ball.Boyd and Winston both face scoring defenses ranked among the top 10 in the country. Clemson (6-0, 4-0 ACC) leads the nation with four sacks per game; only Miami allows fewer passing yards per game than FSU (5-0, 3-0)."(FSU) very well could be the best team in the country," Tigers coach Dabo Swinney said. "Who knows?"The 'Noles statistically have one of the country's best defenses.Louisville, going into Friday, is the only team that has allowed fewer points than FSU (60). The Seminoles have held their four Division I-A opponents to 140 yards and 18.5 points below their averages."Typical Florida State," Swinney said.The Seminoles have dominated with depth. No FSU players rank among the ACC's statistical leaders on defense, but nine players have at least one sack. Six 'Noles have at least one interception, including freshmen defensive backs Jalen Ramsey and Nate Andrews.FSU coach Jimbo Fisher expects them all to be tested by Boyd, who stands eight touchdown passes shy of breaking the conference record of 95, held by former N.C. State star Philip Rivers."I think everybody has to be able to cover everybody," Fisher said. "If you don't, Tajh will just eat you alive."That's what Boyd did last year in Tallahassee when the teams met in a top-10 showdown. He threw three touchdowns, and Clemson scored 37 — the most FSU had allowed in 18 games. The 'Noles needed a career night from their own standout quarterback last season — EJ Manuel — to erase a 14-point second-half deficit and eventually advance to the Orange Bowl.While that stage was big, this showdown looms even larger. The winner of the fourth top-five matchup in ACC history stays atop the Atlantic Division and in the national title picture."I feel like this is a rivalry outside of a rivalry," FSU linebacker Telvin Smith said. "There's always so much intensity around this game."But that rivalry has been one-sided in rowdy Death Valley, where the Tigers have won five in a row over FSU. And while the Seminoles' defense is deep, Clemson is experienced: Its starting lineup features at least 346 games of experience, 162 starts and only one sophomore."It allows your talent to come out," Fisher said. "You play much faster."Even the least-tenured Clemson starter is a star. Defensive end Vic Beasley hadn't started a game before this year, but the 6-foot-2, 235-pound terror leads the nation with nine sacks and is already considered a possible early round NFL draft choice in 2014 or 2015.The Tigers already contained one star quarterback. In Clemson's opener against then-No. 5 Georgia, Plant High alumnus Aaron Murray was sacked four times and had more interceptions (one) than touchdowns (zero) in the Tigers' 38-35 win.If Winston can tame Clemson's defense and earn FSU's first win over a top-three opponent since 2007, the redshirt freshman could vault to the forefront of Heisman conversations."Don't even mention that to him," FSU receiver Kenny Shaw said after Winston threw for five touchdowns and 393 yards against Maryland. "We want him locked in."Especially against the toughest defense he has faced in his life. Matt Baker can be reached at email@example.com.