When Kain Colter showed up for a rookie minicamp in May, he had never caught a punt in his life.

Not in pee-wee ball. Not in high school. Not at Northwestern, where he had played quarterback and some wide receiver.

"Never," Colter said. "I always played quarterback, and they never were going to put me back there."

Now, Colter is trying to learn the craft, and it could play a major role in whether he makes the Vikings as an undrafted rookie free-agent signee.

Colter's quarterback days are behind him as he has switched to wide receiver in his bid to make the NFL. He's also trying to catch the eyes of coaches in training camp with his play on special teams.

"I think all special teams right now will be the key, but I think punt returner is probably my best special-teams thing that I'm doing now," he said. "So I think that will definitely help. I'm definitely improving, but I still have a long way to go."

The 6-foot, 195-pound Colter was an impressive runner at Northwestern, either when lining up as quarterback or hauling in passes. But learning how to catch a punt has been his biggest NFL challenge so far.

He looked pretty good initially when catching balls from the Jugs machine, which simulated the spin off a right-footed punter. But he struggled a bit when he began trying to haul in live balls from left-footed Vikings punter Jeff Locke.