Herb Paterra has been coaching defense for almost four decades. He’s broken down film and schemed up coverages and blitzes at every level. You’d think he’d have seen it all.

But this winter, he met Roy Williams, a safety whom the grizzled old coach simply describes as “special.”

Paterra -- Vandy’s defensive coordinator last season -- spent two months working in Bradenton, Fla., with Oklahoma’s all-world strong safety at IMG’s International Performance Institute, prepping Williams for this month’s draft.

Paterra first broke down six of Williams' game tapes, and then put him through drill after drill to see what the Sooner had -- or more specifically, what he didn’t have. The results? Paterra was blown away by the big man’s nimble feet and ability to change direction, as well as Williams' coverage skills. “Teams could line him up over the slot and bring him as a blitzer or let him drop off in man coverage,” says Paterra. “He has that much ability.”

Folks around the Big 12 already knew that. “With Roy, it was like having 12 guys on the field,” says Oklahoma co-defensive coordinator Brent Venables.

The 6’0”, 222-pound Williams, who won the Bronko Nagurski Award as the nation’s top defensive player last season, was the X-factor in Oklahoma’s devastating defense. The Sooners’ Stoops brothers, head coach Bob and defensive coordinator Mike (a pair of former college safeties themselves) built their scheme around Williams and took the OU program from mediocrity to a national title in two seasons. Whether he was attacking the line in run support or matched out in space on a receiver, Williams seemed to be everywhere the ball was.

Bob Stoops, who coached Jevon Kearse at Florida, says he’s never seen a defensive player dominate a game the way Roy Williams can. Now, the big question is, can Williams do the same things in the NFL?

Paterra says yes. “I coached [former Pro Bowl safety] Bennie Blades with the Lions and Roy is as big and physical as Bennie and has that kind of talent,” says Paterra, “except he is a lot faster and athletic.”

An AFC scout, who has watched Williams for the past two years, thinks he is the best safety prospect to come into the league in 20 years. “Eric Turner went No. 2 [in 1991], and he could run and he could hit. This guy can do both of those things and he is a much surer tackler,” says the scout. “He never misses anyone in the open field, and he’s a great kid with outstanding instincts. He could also probably be a Pro Bowler as a WILL [weakside linebacker] too.”

Normally, the NFL doesn’t think of safeties as impact guys or players worth taking early in the first round. But scouts are re-thinking that because of Williams. They say, just as in baseball, teams are buidling their defenses from the middle out. Just look at what Pro Bowl S Lawyer Milloy did for the Patriots or what Ray Lewis has meant to the Ravens. The model has been established. Last year, the young Bears were led by Brian Urlacher backed by safety Mike Brown on their playoff run.

Entering this year’s draft, Dallas, Minnesota, Atlanta, the Jets, Baltimore, Tennessee and Oakland are all looking for help at safety. Don’t be surprised if Williams is gone by the eighth pick (the Cowboys pick sixth and the Vikings pick seventh).

“Everybody has their own way of doing things,” says Paterra. “But if I had a pick, I’d take Roy Williams.”

Bruce Feldman covers college football for ESPN The Magazine. E-mail him at bruce.feldman@espnmag.com.