MANKATO, Minn. -- The Minnesota Vikings' safety spot next to Harrison Smith might be one of the few truly open jobs on the team's defense during training camp, and it doesn't sound as though the Vikings are in any rush to settle on a player. Coach Mike Zimmer said last month the job would be decided during training camp, and cautioned on Wednesday it's hard to fully evaluate a young safety without game action.

"All these things will get determined when we get into the preseason games," Zimmer said. "Especially for safeties, they have to be able to make checks and movements and things like that and all this."

The coach offered that response to temper expectations of second-year player Antone Exum, whose name general manager Rick Spielman offered up in a discussion of the Vikings' safety candidates after the draft. The converted cornerback played mostly special teams after being drafted in the sixth round a year ago, and seemed in need of maturation after arriving from Virginia Tech.

While the Vikings need to see more from Exum before determining whether he can start, Zimmer said he's noticed a change in the safety.

"We had a couple of guys last year that came in here as rookies that really didn't know how to act. He was actually one of them. He has grown up a lot," Zimmer said. "Now, it seems important to him. It seems like he's understanding what the coaches want, want we want to do, what [defensive backs coach] Jerry [Gray]'s trying to get done with him."

The Vikings will have to pick between Exum, undrafted rookie Anthony Harris and holdovers Robert Blanton and Andrew Sendejo for the other spot, and early in camp, they've kept Blanton next to Smith in the first-team defense. Exum, though, might have the best range of the bunch, and could get a chance to play his way into the job.

"He is a good athlete, he is improving every day, he's working real hard," Zimmer said. "He has proven to me that it's a lot more important to him. Some guys, they come into the league and they think they've made it and they don't understand what you have to do to become a professional football player. I had several talks with him, but finally I think he has figured this stuff out a little bit."