UNIVERSITY PARK, Pa. -- Before the season started, the defensive secondary faced the most questions. The players routinely discussed how they heard outsiders' doubts and how they acknowledged the need to mature.
Six games in, the secondary has not turned into a force but it has not been a major weakness of late. Penn State's passing defense ranks sixth in the Big Ten, giving up an average of 212.3 yards per game.
Two key changes, along with the emergence of Stephen Obeng-Agyapong, have helped Penn State in the past four games, all victories.
Those first two games -- both losses -- weren't pretty. Ohio passed for 324 yards, most of them in the second half. Virginia threw for 263 yards, the holes in the passing defense never more obvious than on the Cavaliers' last drive, when their quarterback, Michael Rocco, completed five-of-five passes for 91 yards.
Cornerback Stephon Morris called out the secondary after that game. He said their weaknesses, especially on third down, had failed the team.
Since then, Penn State has allowed an average of 171.75 passing yards per game. Only Illinois has had more than 200 against the Nittany Lions in the past four games.
"It's more intense, a lot more communication and better energy going toward it," safety Malcolm Willis said.
The passing defense has provided new looks these past four games. Obeng-Agyapong, a safety, increased his role, finishing second on the team in tackles against Navy and getting a pass breakup and tackle for loss against Temple.
On third downs, the complexion of the passing defense has changed. Linebacker Mike Hull generally replaces Glenn Carson. Freshman Da'Quan Davis enters as a cornerback, while cornerback Adrian Amos moves to safety. His versatility has been praised since August.
"It's benefited us greatly because we've been able to get off the field in those situations," Willis said. "That just speaks to the athlete he is. He's able to play almost any position on the field. His athleticism is a plus to us."
The Northwestern game provided the improved secondary's biggest test to date. After throwing for 310 yards last week against Indiana, the Wildcats had 135 yards through the air against Penn State. They didn't complete a pass longer than 6 yards until the final two minutes of the first half.
The game provided a benchmark for how far the passing defense has come since early September.
"Everyone knows how hard that offense is to stop," cornerback Stephon Morris said of Northwestern. "They always have these good quarterbacks. ... It means a lot to this defense."
• Game: Penn State at Iowa, 8 p.m. Oct. 20.
• TV: Big Ten Network.
Pass defense in the Big Ten
Rk Team Avg/G
1 Michigan 155.0
2 Nebraska 177.8
3 Minnesota 181.6
4 Michigan State 186.3
5 Iowa 204.0
6 Penn State 212.3
7 Purdue 219.4
8 Wisconsin 223.3
9 Illinois 226.8
10 Indiana 246.2
11 Ohio State 265.3
12 Northwestern 287.8psusports
Mark Dent: email@example.com and Twitter @mdent05.