Zach Zwinak is the man of the moment for Penn State at tailback

Penn State's situation at running back since the end of spring practice has evolved in ways that no one, not even coach Bill O'Brien, could have predicted.

The Nittany Lions adjourned for the summer with Silas Redd, a 1,000-yard rusher in 2011, being counted on to take most of the carries. Converted wide receiver Bill Belton was the top reserve, while 232-pound redshirt sophomore Zach Zwinak was on the fourth string.

However, a tailback shuffle began when Redd transferred to Southern California after Penn State was hit by NCAA sanctions. Belton started the opener against Ohio but suffered a sprained ankle and missed the next three games. And now Zwinak, the former No. 4, has become the main man in the backfield.

Zwinak, a self-described "nervous kind of guy" before kickoff, posted his fourth 100-yard rushing game of the season Saturday against Nebraska. His career-high 141 yards included a 50-yard touchdown run, Penn State's longest play from scrimmage.

"We had a much different football team after the Blue-White Game than we do as we sit here today," O'Brien said Tuesday. "Silas Redd was here. We moved Billy Belton there. We had injuries occur, and as injuries occur, the next guy has to step up.

"That's what happened with Zach. We had injuries and he was the next guy. He came out and he did a nice job of doing what we coached him to do. He's a tough kid. He can run. He's faster than people think he is. He's strong, a punishing runner."

Even though he sat out two of the first three games, Zwinak has rushed for 686 yards going into Saturday's home contest against Indiana. He has averaged 98.3 yards in Big Ten games, ranking him sixth in the conference.

He's not perfect. Zwinak lost a first-quarter fumble inside Nebraska's 10-yard line, the third time he has turned the ball over in the last four games.

"He's got to get better at ball security," O'Brien said.

O'Brien said that at a crowded position such as tailback, where seniors Michael Zordich and Derek Day are also in the mix, the starter is the man who practices the best during the week. After starting the last two games, Zwinak appears to have established some separation on the field.

Belton, a former Winslow Township High School star, started against Illinois in his first game back after his injury. Two weeks later, the sophomore had career highs of 103 rushing yards and three touchdowns at Iowa.

But he has been invisible the last two weeks, with just one carry - a 1-yard loss at Nebraska.

"I think he's competing well," O'Brien said. "I think it's a matter of, we've got a guy in Zach Zwinak who's rushed for close to 700 yards and has had some good games, and we've just stuck with him."

Zwinak, however, knows the situation can change at any time.

"I come into each week now knowing what's going to happen," he said, "if I'm going to get carries, if someone else is going to get carries, if we're going to pass the ball. So you just try to be ready."

McGloin nominated. Penn State quarterback Matt McGloin was one of 50 players nominated for the Burlsworth Trophy presented to the nation's outstanding football player who began his career as a walk-on. Created in 2010, the award is sponsored by the Springdale (Ark.) Rotary Club.