Of all the reasons the Vikings defense has propelled a 5-2 start, it's been the play of the secondary that has provided the greatest encouragement. The return of cornerbacks Chris Cook and Antoine Winfield, the arrival of rookie safety Harrison Smith and the consistent energy provided by Jamarca Sanford have all put the Vikings in position to be pretty formidable against the pass.

With Week 8 now here, the Vikings rank 10th in the NFL in pass defense, allowing just 219.4 yards per game. They've done so even as they've registered four of their five wins without trailing.

Yes, Winfield seems rejuvenated at age 35, playing with incredible energy at all times. But on Tuesday, Vikings coach Leslie Frazier singled out Cook as a player who's quickly ascending.

"I think his confidence has just grown," Frazier said. "Early in the season, I thought he was coming along, but he has really taken a leap over the last two or three weeks. I've been very, very impressed with the progress he's made."

Cook played a big role in helping to limit Arizona's Larry Fitzgerald to four catches and 29 yards Sunday. Now he'll get another big test Thursday night against Tampa Bay's Vincent Jackson.

A year ago, Cook was arrested after a domestic dispute with his then-girlfriend. The Vikings exiled him from the team for the final 10 games of 2011 but always hoped Cook would get back in the mix. Now, he's taking care of his business.

Said Frazier: "There was a transition for him getting back and playing and getting up to the level that we thought
he was at about this time a year ago. But his confidence has grown. A lot of that has to do not only with the success he is having in practice, but also what he's doing in the games. We feel like he can match up with
some of the best receivers in this league."

Frazier said defensive backs coach Joe Woods has consistently challenged Cook to play to his potential. Cook's combination of size -- he's 6-foot-2 and 212 pounds -- and quickness makes him a weapon.

"We drafted him because of his size and his length and his speed and his football IQ," Frazier said. "It's been a matter of time for him getting the reps because he's still a guy that doesn't have a long resume when it comes to starts. The more time on task he gets the better it seems he's performing."