Madieu Williams: Safety precautions

The Vikings thought enough of rookie safety Tyrell Johnson that they traded up to select him in the second round of the NFL draft. They didn't, however, envision him taking on a prominent role so early in his career.

The plan changed when high-priced free agent Madieu Williams suffered a neck injury early in training camp. Williams could miss the first three regular-season games, meaning Johnson will start the opener at Green Bay on Monday night.

"That's not my first preference or my first wish, if you will," Vikings coach Brad Childress said. "You know what? That's why we drafted him where we drafted him. Some guys get to get in there quicker than others."

The question is, will the Vikings experience a dropoff with Johnson filling in for Williams? The Vikings signed Williams to a six-year, $33 million contract (including nearly $13 million in guarantees) this offseason to replace Dwight Smith in an effort to improve the secondary and pass defense, ranked last in the NFL in 2007.

Williams, who played cornerback and safety in four seasons with the Cincinnati Bengals, is known primarily for his cover skills. He has enough speed and athleticism to cover a pass-catching tight end or line up across from a wide receiver.

"Any time you have a safety who can come down and cover a third receiver or a tight end, especially a team that does a lot of three- or four-wide sets, it definitely plays to your advantage," Williams said. "You don't have to substitute a lot, especially when they go no-huddle. You can just drop one of the safeties, and he can cover one of the guys."

The Vikings hope to maximize Williams' versatility by moving him around in coverages, particularly in third-down situations. His cover skills also should allow veteran safety Darren Sharper to freelance and take more chances, going for interceptions.

"[Williams] gives us some flexibility from a coverage standpoint, whether we're playing Cover-2 or a man coverage," defensive coordinator Leslie Frazier said this offseason. "He can do both and do them very well."

The Vikings might be forced to play things closer to the vest with Johnson, at least initially. The coaching staff likes Johnson's mental makeup and his athletic ability. He also brings a physical presence that should help in run support. But he has yet to play a game, so it's hard to gauge how he will react when the regular season starts.

"He's a quick study," Childress said. "He's sharp. He's up to speed on what's happening in the playbook. His see-to-do is very quick, and obviously he has good range and will strike you."

Defensive backs coach Joe Woods said the scheme won't change because of Johnson's inexperience.

"Each guy has their own strength, and Tyrell is the same type of guy," Woods said. "He has great speed, he can cover, he's just a rook. That's what you lose is experience."

Johnson admits it's been a difficult transition learning the Tampa-2 defense, but he's confident he can handle this responsibility, even if it's more than anyone expected from him this soon.

"Everything I do I try to be the best at, no matter what it is," Johnson said. "Just working hard at the job and the role they've given me and do the best I can with that."