Kirk Ferentz admitted he never had heard of Bill O'Brien.

That was until four years ago when Ferentz's oldest son, Brian, was hired by the New England Patriots and started working with O'Brien.

"I didn't know Bill O'Brien from Bill Glass," Ferentz said. "When my oldest boy first started telling me about Bill and the kind of coach and person he was, that got my attention."

The two will coach against each other for the first time Saturday night when Penn State and O'Brien take on Iowa and Ferentz in Iowa City.

The Nittany Lions and the Hawkeyes are 2-0 in the Big Ten and 4-2 overall after slow starts.

"Nothing has really surprised me about the way things have gone (at Penn State)," Ferentz said. "Bill has been put in a real unique position, and I would suggest challenging, too. He and his players have done just a tremendous job."

O'Brien and Ferentz served as assistant coaches under Bill Belichick, Ferentz with the Cleveland Browns in the 1990s and O'Brien with the Patriots the last five seasons. Brian Ferentz, like O'Brien, left New England after last season and joined his father's staff as offensive line coach.

They learned many of the same coaching principles from Belichick.

"I don't want to speak for Coach Ferentz or for Brian," O'Brien said. "I'll speak for myself. I would tell you that it (the common bond) is the discipline of the teams. Hopefully we're not penalized a lot and hopefully we don't turn it over a lot. We try to create a physical environment in practice and work on situational football.

"When you watch Iowa, you see a very tough, physical, smart team that doesn't beat itself. We've got a very big challenge going against them."

Ferentz said he's biased when it comes to O'Brien. Brian Ferentz worked as an offensive assistant with O'Brien and then under him with the Patriots. When O'Brien became offensive coordinator last season, Ferentz moved up to coach the tight ends, notably Rob Gronkowski and Aaron Hernandez.

"I'm just so appreciative of him," Kirk Ferentz said. "Bill's not only a great teacher, but also a great mentor. My son asked a lot of questions. He's very inquisitive. And Bill always found time for him and taught him. He helped him grow.

"On a personal level I can't repay him enough for that."

Ferentz also is impressed that O'Brien worked under George O'Leary at Georgia Tech and Ralph Friedgen at Maryland, whom he called "great college coaches." He also admires him for joining the Patriots staff in 2007 as one of the low men on the totem pole and taking a pay cut.

"He gave up a lot of security and a lot of things most people wouldn't walk away from to go up there without any guarantees," Ferentz said. "I think that tells you a lot about the kind of person he is and the kind of coach he is.

"That was all about him wanting to learn, grow and develop."

O'Brien eventually moved up to coach the Patriots quarterbacks, including future Hall of Famer Tom Brady.

"People may be aware of what he did in New England, which was just phenomenal," Ferentz said. "But coaching a veteran quarterback (Brady) who's established, that's one of the hardest jobs in the world."

O'Brien said he and Brian Ferentz remain great friends. He said he also has great respect for Kirk Ferentz, who praised O'Brien at the Big Ten Kickoff in July and this week.

"Bill has done it at every level with success," Kirk Ferentz said. "He's coached the option. He's coached a lot of things. Then he took the Patriots to a level where they set records a year ago. His depth of knowledge is real important to college coaching.

"He's a tremendous person. To have him working with young people is a great thing for them. It was just a great hire by Penn State, unfortunately."