He grew frustrated with lacrosse and although he says he wishes he'd stuck with it, things seem to being working out for the junior, who has transitioned from a reserve running back into a starter at fullback in five of Penn State's 11 games.
The choice between the two sports required that he leave public school and enroll at St. Anthony's, a Catholic school in Huntington, N.Y., where he emerged as the New York Daily News' Player of the Year in 2003 after winning three state championships.
In those days, he was a running back, a position he was recruited to play for the Nittany Lions. But with Tony Hunt, Austin Scott and Rodney Kinlaw perched above him on the depth chart, it became clear that the Dix Hill native needed a switch.
To learn the new position, he asked the linebackers what he could do to make their jobs more difficult. He took notes.
I don't think it's been too much of a challenge, he said. A lot of it is how you attack it and leverage. I talked to [Dan] Connor and things like that. It depends on how a fullback comes at you depending on angles being a guy that can get in your way, a guy that can stay with you. It hasn't been a problem at all.
He's not the biggest fullback on the roster (6-foot, 230 pounds) nor is he the best blocker - often two necessities for the position. Those honors belong to 6- 1, 242-pound senior BranDon Snow, who came into the season as the returning starter for the defending Big Ten champs. In 2005 Hahn was mostly confined to special teams duty, where he may be best known for falling on Donnie Johnson's blocked punt in Michigan State's end zone to give the Lions a 10-0 lead, helping to clinch the conference title.
But Snow was benched for the season-opener due to an unspecified violation of team rules, and Hahn went on to start the first two games. He has been a key contributor on the offense ever since, even after Snow returned. The two now share the position.
Hahn is plays like Larry Centers; he's a shifty runner with an ability to catch the ball out of the backfield. Snow is the more-trusted blocker. Although Hahn finds the ball in his hands less often that he was accustomed to as a tailback in high school, he's still effective.
Last Saturday against Temple, Hahn ran a flat route toward the Owl sideline on a third-and-4 play in the third quarter. Anthony Morelli hit him with a pass and Hahn picked up eight yards along the sideline, sustaining the drive. Hunt scored on a screen pass eight plays leader, increasing the Lions' lead to 38-0.
Through repetition, Hahn's blocking abilities have improved. Over time, he's grown to appreciate leveling a linebacker or clearing out a lineman so somebody else could find pay dirt.
At this point it's pretty much the same as scoring a touchdown, he said. It's my role, it's something I've accepted, and it's something I've grown to like doing. It's the same as catching a pass or taking a ball up the middle and scoring.
Receiving offers from Maryland, most of the Big Ten schools and Stanford, among others, he opted for blue and white in his junior year of high school. If he had chosen a different school, it's not clear where he'd be in the backfield.
Still, he has no regrets.
Of course, being a player, I think that I can help the team anytime I get the ball or anything like that, Hahn said. But I'm happy with my role and I'm happy with the opportunities I've been given. So, I can't really complain there.