It's easy to forget how inexperienced the Iowa defense was coming into this sea-son.

You think Mitch King and Matt Kroul, the Hawkeyes' four-year starters on the defensive line, and assume it's a veteran group that is out there shutting down opposing offenses. But there were six seniors lost off last year's unit, which ranked in the upper half of the Big Ten in most statistical categories.

Playing with first-year starters at defensive end, cornerback, both inside linebacker spots and strong safety -- and just three seniors in the starting lineup -- Iowa has improved across the board, ranking in the top three in the Big Ten in everything that matters.

"Guys are playing at a high level," said coach Kirk Ferentz, whose Hawkeyes travel to Illinois today. "We're playing steadily on defense right now, and that's a sign that we're doing some things well."

Iowa (5-3, 2-2 Big Ten), which won two straight before a bye week, ranks second in the Big Ten and fifth in the nation in scoring defense, surrendering only 11.5 points a game. The Hawkeyes are third in the conference in total defense (297.8), rushing defense (105.8) and passing defense (192.0). All of those statistics are ahead of last year's pace.

"We feel good, but we don't feel comfortable," linebacker A.J. Edds said. "There's a difference. We know we've done some good things, but our best football is still ahead of us."

Illinois (4-4, 2-3) will challenge Iowa's defense in ways it has yet to be challenged. The Hawkeyes have shut down running teams and held passing teams out of the end zone, but they've yet to face a team that can do both.

Led by junior quarterback Juice Williams, the Illini can do both with proficiency.

Williams leads the Big Ten and ranks eighth nationally in total offense. He throws for 271 yards a game and adds 60 on the ground, and he has plenty of talent around him, starting with sophomore wideout Arrelious Benn.

"These guys are very, very prolific right now," Ferentz said, "very talented, very veteran. And they're led by a quarterback who is a proven winner."

For Iowa's young defense, this is a chance to solidify the numbers that suggest it is one of the best in the country. The Hawkeyes won't see a better quarterback this season. The Big Ten does not house a more explosive offense.

"We just have to be ready for anything," Fletcher said. "They can run anything they want this weekend, and we've got to be ready."