Last summer, Penn State's defensive backs used outside criticism for motivation.

The Lions' secondary had to replace all four starters and Malcolm Willis and Stephon Morris reminded everyone of the gloomy forecast many had for the back four. "We're supposedly the worst unit on the team," Willis told his teammates after practices. "Everybody is doubting us, everybody is doubting our ability."

There are fewer doubts heading into the 2013 season. In fact, the secondary could be branded a potential strength for a defense that loses All-Big Ten performers up front (DT Jordan Hill) and at linebacker (Michael Mauti, Gerald Hodges).

Penn State returns both starters at safety from 2012 in Willis and Stephen Obeng-Agyapong, as well as Adrian Amos, who started at cornerback last fall but moved to safety in the spring and is listed as a starter on the team's latest depth chart. The safety group also includes Ryan Keiser, a reserve in 2012 who head coach Bill O'Brien labels a potential unit leader this season.

"We feel like we have better depth there than we had last year, and we've got a good amount of returning experience," O'Brien recently told ESPN.com. "And they're very well coached. That position has to be very well coached."

O'Brien credits defensive coordinator John Butler, the team's secondary coach in 2012, for pushing the right buttons with the personnel in the back four. This spring, the coaches moved Trevor Williams and Malik Golden from wide receiver to cornerback and safety, respectively. Williams emerged from the spring as a starter.

The Lions are undoubtedly younger at cornerback than at safety -- all players listed on the summer two-deep are freshmen or sophomores -- but they have flexibility with Amos, who had 44 tackles, two interceptions and three pass breakups last season.

"He's got to be ready to play a lot of different roles for us," O'Brien said. "He's a very valuable member of our team."