Zettel's all-around athleticism makes him one of the best defensive tackles not just in the Big Ten, but in the country.
The senior from Michigan can also knock down a tree with a shoulder tackle, though he admits that was a skill best left undiscovered. The video of Zettel lining up in a three-point stance and taking down a dying tree in the woods went viral this offseason.
''It wasn't the smartest thing I've done,'' Zettel said Friday at Big Ten media days. ''It didn't feel good on my shoulder, so I'm glad I didn't get hurt. But it happened. We evolved on things we wish we didn't do.''
Zettel spent last season treating ball carriers and offensive lineman like that tree. He had 17 tackles for loss, including eight sacks, anchored one of the top defenses in the nation and was named All-Big Ten.
''He's a combination of traits,'' coach James Franklin said.
Franklin said he likes to ask his players things such as who are the best basketball players, best golfers and toughest guys on the team. Zettel is on every list.
''He does some things athletically that guys his size don't normally do,'' Franklin said. ''And then some guys have that but they don't have the mentality to go with it. Just like he's a unique athlete, he's kind of a unique guy. He's somewhat strange in a lovable way.''
Franklin added, ''He's one of those guys you love to have on your team because he keeps it light and he keeps it interesting and he has a lot of fun.''
The one area where Zettel's game was lacking last season was turnovers. He forced only one fumble and wants to improve on that.
''I want to start striking the ball more, aiming for the ball,'' he said. ''Plus I want to emphasize on getting off blocks better.''
At 6-foot-4, 274 pounds, Zettel is on the small side for a defensive tackle, but along with 322-pound Austin Johnson, Penn State should be solid in the middle again this season.
''I think him an AJ are as good of a combination of two defensive tackles in the country,'' Franklin said. ''To be honest with you, I don't know if Zettel is who Zettel is without AJ. I don't know if AJ is who AJ is without Zettel.''
No more knocking down trees though.
''Although it's interesting and fun (to see),'' Franklin said, ''it's not real comforting.''
Follow Ralph D. Russo at www.Twitter.com/ralphDrussoAP