The torn ACL was hard enough to deal with. When Zach Zwinak finally did get to return to practice a year later, things didn't get much easier.
As a redshirt freshman in 2011, Zwinak served as a tailback on the scout team. His weekdays were spent helping prepare Penn State's smothering first-team defense, taking hit after hit from the likes of Gerald Hodges, Michael Mauti, Devon Still, Jordan Hill, Nate Stupar and Glenn Carson.
I like to joke around with him that we made him tough, said Carson, Penn State's starting middle linebacker.
In the past month, other Big Ten defenses have been discovering just how tough.
Zwinak has racked up 590 of his 686 rushing yards in conference play. Installed as the Nittany Lions' feature back these past two weeks, the sophomore set new career highs in each game with 134 yards at Purdue and then 141 last week at Nebraska.
With Indiana up this week, bringing along one of the nation's worst rushing defenses into Happy Valley, Zwinak has a shot at setting a personal best for the third straight game.
I came into season with no expectations, the soft-spoken Zwinak said. Everything changes week-to-week. I just try to step up and play the role they ask me to play.
On Saturday, that role figures to be large indeed.
The Hoosiers enter the game allowing a stunning 244 yards per game on the ground, ranking them 118th out of 120 FBS teams. Last week, with a spot in the Big Ten title game on the line, Indiana somehow surrendered 564 yards rushing to Wisconsin in a 62-14 loss.
For the first time this season, Zwinak was listed as the lone starter on the team's depth chart, though the Maryland native said that, just like every week, playing time will be dependent on practice.
Effort hasn't been an issue for Zwinak, who overcame that ACL injury back in October 2010, his first year on campus.
He's a tough kid, Lions coach Bill O'Brien said. He can run. He's faster than people think he is. He's a 235-pound guy and he's strong. He's a punishing runner.
And are there things that he needs to get better at, of course. He's got to get better at ball security. He can be a really good route runner if he concentrates on it, and I know he will. He's been a guy who has done a great job for us this year.
Zwinak, who was ranked as the nation's top fullback recruit coming out of high school, has rounded out his game and is actually fifth on the team with 16 catches.
Surprisingly, Zwinak actually has more yards from scrimmage this year (842) than former Lions starter Silas Redd (831), and it's the receiving yards that have given him the edge. Redd has just six catches while also splitting time in the backfield at USC.
Zwinak said he was most concerned about getting his speed back from the torn ACL. He got to show off his top gear against the Huskers, outrunning the defense on a 50-yard touchdown up the middle.
Also on display, however, was one of his biggest issues, losing his third fumble in the last four games.
Coming into the game, I'm a nervous kind of guy, Zwinak said. But once the game starts getting going, I don't notice it anymore. It's just playing football like you have your whole life.
The most recent fumble came in the red zone in the first quarter, taking away a scoring opportunity. It landed Zwinak on the sideline for the next few drives with Michael Zordich taking his place.
Fellow sophomore Bill Belton, meanwhile, has just one carry in the last two games. That has opened the door for Zwinak to finally give the Lions a consistent threat in the backfield.
I can't speak for the whole team, but for me it's been an exciting year, Zwinak said. It's been interesting considering everything that's happened. We haven't had the greatest situation, but we've stayed together, we've played for each other. And that's all we need.
Indiana at Penn State
Noon Saturday, Big Ten Network