ATLANTA -- The expression on the face of Chris Simmons was one of surprise, or to be exact, the Georgia Tech outside linebacker was taken aback by a questioner.

The Yellow Jackets' defense carries this team, doesn't it, Chris?

"Our offense is really good," said Simmons, slipping into his diplomatic mode.

"Our offense is really, really good. Really. We know they're really good."

Simmons smiled, then mentally slapped himself in the face. He knows what the rest of country and No. 1-ranked Virginia knows: The Georgia Tech defense is the foundation of the team. It has been mostly responsible for the 6-0-1 record and No. 16 Associated Press ranking. The Yellow Jackets have ridden a black-and-blue defensive wave of punishing hits and a pass defense that ranks second in the country. It will face its biggest test Saturday, 2:28 p.m. kickoff, when it faces 7-0 Virginia for ACC supremacy at Scott Stadium in Charlottesville.

A Virginia win doubtless would gain the Cavaliers more respect among some of the poll voters who aren't sold on them yet, though Virginia did receive 44 of 60 first-place votes in this week's AP count. A Georgia Tech win would position the Yellow Jackets for a possible top 10 ranking.

The Cavaliers have massive firepower evidenced by the top-ranked offense in the country, averaging 48.1 points and 544.9 yards per game, national highs. Quarterback Shawn Moore has thrown for 1,573 yards, putting Virginia third in the ACC, and his 18 passing touchdowns are more than North Carolina State, North Carolina and Clemson's combined total (16).

Virginia's perpetual motion machine will collide with a defensive wall of muscle and moxie.

It's not that the Yellow Jackets' offense is bad. It's just that it doesn't grab the game by the throat the way Georgia Tech's defense does. The Yellow Jackets have played four Division I-A teams with winning records and averaged 23 points against them. The defense allowed only 10.2 points to those teams.

"I'm biased but I guess that's how it is," Simmons said. "We do usually control the game. The defense knows what its role is and how important our play is for us to win the game. Our outlook is, if they don't score they can't win. If our offense doesn't score, we're going to score."

The focal point of the Yellow Jackets' defense is junior free safety Ken Swilling, who is difficult to miss. He's the one built like Mr. Universe and with the speed of a 400-meter sprinter. He's also one of the hardest hitters in college football. NFL scouts say Swilling could be a top-five pick should he come out early. If he stays for his senior year, he could be No. 1.

But this week all that's on Swilling's mind knocking the blue and orange out of some Cavalier.

"We feel like we try and go out to set the tone early in a game," Swilling said. "When we get the chance to go on the field first, it really gets things going. We try to make the game as physical as possible on the first series. It's very important on the first series to go out and hit somebody and set the tone.

"This game is important to me. Not only are there ACC implications but there are national implications. This is a test for me and the entire defense. We haven't faced a team that both passes and runs the ball very well. They do everything well. Everyone likes to talk about our defense and we think of ourselves as a pretty good defense. Well, it's time to show what we can really do. It's time to come play."

It seems Swilling has always come to play, but not always on defense. When he was a wiry freshman at Stephens County High School in Toccoa, Ga., Swilling played running back. Eventually he was ranked as one of the top three recruits in the state. Except Swilling was known more for his running skills, rushing for 920 yards his senior year.

But one season earlier, during the first practice of his 11th-grade year, he replaced an injured free safety during a three-on-three drill. It was then he first experienced the rush of tackling someone. He liked -- no, loved -- the feeling of hitting instead of being hit.

"I started hitting," he said. "I couldn't have enough. I didn't want to go back on offense. My senior year I played a little offense, but I hated it. I wanted to hit." He never left the free safety spot, and his final year in high school he had five interceptions and averaged six tackles per game.

Today, the work Swilling has put into his physique is more than evident. The man is huge, but it is a sculptured huge. Listed at 6 feet 3 and 230 pounds, he bench-presses 405 pounds and scouts say his 40-yard dash time is between 4.55 and 4.6 seconds. He is in the mold of the 49ers' Ronnie Lott or Denver's Steve Atwater: a big hitter who can also cover.

"He is one of the best defensive backs in college football," said Georgia Tech Coach Bobby Ross, who is obviously biased but whose opinion is shared by many college and NFL coaches.

"Ken adds something to us other than just his playing ability," Ross said. "There are some other things that are involved. He's a great leader. He's a guy that is a very imposing-type figure. He has great range and is one of the toughest tacklers I've ever seen. He tackles like a linebacker."

Swilling has missed the last two games because of a sprained ankle -- he is healthy now and has been practicing all week -- but his statistics are still impressive. He leads the ACC with four interceptions in five games. He has been in on 35 tackles.

The Yellow Jackets' 3-4 defense has very few weaknesses, and its linebacking group of Marco Coleman and Marlon Williams on the outside with Jerrelle Williams and Calvin Tiggle (Friendly High School) on the inside is second-best in the ACC against the run (103.9 yards a game, ranking 12th nationally). Coleman, a sophomore, leads the conference in tackles (60) and quarterback sacks with 8 1/2.

"What makes this defense good is that we've seen just about everything," Coleman said. And that includes the no-huddle offense, which Duke used last week for the first time all year.

Incredibly, Georgia Tech had not given up a passing touchdown until a couple of three-yarders in its 48-31 victory over the Blue Devils. A 71-yard touchdown drive by Duke was the season's longest against the Yellow Jackets; the longest previous had been 40 yards by Clemson.

And this is an interchangeable defense. When any part is missing -- except Swilling and Coleman -- the Yellow Jackets' depth can pretty much make up for it. When Coleman hurt an ankle and temporarily left the Duke game in the fourth quarter, his backup, Simmons, came in and hit quarterback Billy Ray so hard his helmet went airborne.

"That's what you need to have a good team," said cornerback Willie Clay. "You need depth. We have players on defense that can come in and play at any given moment."

Said Simmons: "A lot of the guys on defense have been playing together for three years. That's what makes us good. We don't have a lot of individuals. We all just play together. Before a game, you'll see us hugging and carrying on. The whole D is like that."

Clay called the last two weeks -- in which they tied North Carolina, 13-13, then allowed 3-5 Duke to bulldog for 375 yards in total offense -- uncharacteristic and said maybe the Yellow Jackets had been guilty of looking ahead to the Virginia game.

"I guarantee you Saturday we'll be ready to play," Clay said. " . . . Get on with the game."