STATE COLLEGE — After three underwhelming nonconference wins to start the year, it was hard to tell just how good Penn State was going to be.

Iowa's defense and special teams provided a resounding answer Saturday night, yet again using the Nittany Lions as a springboard to success.

"It lets us realize that we're capable of being a good team," said linebacker Pat Angerer, who led Iowa with 14 tackles, a forced fumble and an interception.

Iowa has won eight straight since upsetting then-undefeated Penn State, 24-23 last November in Iowa City to hand the Nittany Lions their first loss and knock them out of the 2008 national title chase.

The latest upset sent Iowa (4-0, 1-0 Big Ten) rocketing back into the latest AP Top 25 poll at No. 13 after being unranked for two weeks, while Penn State (3-1, 0-1) tumbled 10 spots to No. 15.

The Hawkeyes' offense could use some work after stumbling themselves against Penn State in a defensive slugfest played in pouring rain. Iowa receivers dropped several passes, and the offensive line got caught off-guard when the Nittany Lions blitzed more in the second half.

Normally cool Penn State quarterback Daryll Clark looked out of rhythm, his offensive line harassed by the Hawkeyes defensive front. The Lions turned the ball over three times as their offense sputtered.

"I don't know. I have to look at the tape before we start saying this is what happened," coach Joe Paterno said. "Obviously we'll see that turnovers were a big thing in the game."

Clark started out hitting his first five passes, including a 79-yard touchdown catch by Chaz Powell, but finished 12 of 32 for 198 yards with three interceptions.