Kirk Ferentz couldn't help but think back to Oct. 19, 1985. As Iowa's offensive line coach 36 years ago, he was involved in one of the most memorable games in Hawkeyes history.

No. 1 Iowa defeated No. 2 Michigan on Rob Houghtlin's 29-yard field goal as time expired, 12-10, setting off a celebration for the ages at Kinnick Stadium.

"I'll remember that as long as I live just because of the environment that day,'' said Ferentz, now in his 23rd year as Iowa's head coach. "Not everybody gets that chance. It's a pretty cool thing.''

Another of those "pretty cool things'' will play out Saturday afternoon (3 p.m., FOX) in Iowa City, where the third-ranked Hawkeyes are host to No. 4 Penn State in the matchup of the year in the Big Ten so far. Both teams enter the tilt with 5-0 overall records and 2-0 marks in the conference, and the outcome certainly will resonate deep into November if not all the way to January.

It marks the first time since Nov. 24, 1962, when Wisconsin topped the Gophers 14-9, that a top-five matchup between Big Ten teams does not include either Michigan or Ohio State.

"This is a tremendous opportunity that we're excited about,'' Penn State coach James Franklin said.

Both teams in Saturday's showdown feature a rugged, opportunistic defense. Iowa ranks second nationally in scoring defense, allowing 11.6 points per game (trailing only Georgia's 4.6). Penn State is third at 12.0. The Hawkeyes lead the nation with a plus-12 turnover margin, with the Nittany Lions tied for 10th at plus-6.

Franklin described Iowa's defense as "simplistic,'' and he was quick to clarify that's meant as a compliment to Hawkeyes defensive coordinator Phil Parker.

"That's what the smartest people in the world do: They take complex things and are able to present them in a very clear and precise manner,'' Franklin said. "… They spend their time studying you, rather than what their checks might be.''

You can't argue with the results. Led by that defense and its sticky fingers, the Hawkeyes started the season by dominating two of the preseason pollsters' darlings, No. 17 Indiana and No. 9 Iowa State. They thrashed Indiana 34-6 as defensive back Riley Moss returned two of Michael Penix Jr.'s three interceptions for touchdowns. A week later in Ames, the Hawkeyes intercepted QB Brock Purdy three times, prompting coach Matt Campbell to bench the All-Big 12 senior, and got a fumble return TD in a 27-17 win.

The latest to feel Iowa's wrath was Maryland, which entered last Friday's game in College Park with a 4-0 record but left a beaten mess after a 51-14 loss. Terrapins QB Tulia Tagovailoa had thrown one interception entering the game. The Hawkeyes picked him off five times and had seven takeaways overall.

"Their scheme more times than not allows them to capitalize on mistakes because they have their eyes on the quarterback as much as anybody in college football,'' Franklin said.

Penn State is doing it with defense, too. The Nittany Lions opened with a 16-10 win at Wisconsin in which they withstood 95 offensive plays from the Badgers. A stirring, 28-20 win over Auburn followed, and last week the Lions blanked Indiana 24-0.

"You're playing an established program,'' Ferentz said. "If you're not ready to play, it can be embarrassing, so you better get ready to play.''

Franklin knows that Kinnick Stadium, with its tight sidelines, will be frenzied. "They are right on top of you,'' he said. "It's a tough environment, and we're looking forward to it.''

As is Ferentz.

"It's what you want to play for,'' he said. "It's fun when the chips are on the table.''