TUCSON, Ariz. (AP) Wanting a defense to match the unpredictability of his innovative offense, former West Virginia coach Rich Rodriguez decided on a scheme that would employ three linemen and five players in the secondary.
To get an idea of how it might work, he took his staff on a tour of the South.
The first stop was Wake Forest to get a look at defensive coordinator Dean Hood's 3-3-5 formation. Next, they went to South Carolina to talk with Gamecocks coordinator Charlie Strong, also using five defensive backs in his base defense.
After that, it was on to Mississippi State to see Joe Lee Dunn, widely credited as being the father of the 3-3-5.
Rodriguez and his coaches then headed back to Morgantown and started working on their own version of the defense.
``We started studying it, took what we wanted from everyone else's ideas and it evolved from there,'' said Tony Gibson, a member of Rodriguez's staff at West Virginia from 2001-07. ``We just kept building it.''
Rodriguez stuck with the 3-3-5 defense, bringing it with him to Arizona, where he's in his first year and Gibson is his assistant head coach.
They're not alone.
A handful of teams across the country are using the 3-3-5, a version of the more familiar nickel defense designed to keep up with the influx of spread offenses in college football.
Jeff Casteel, Rodriguez's former defensive coordinator at West Virginia, is in charge of running the five-defensive-backs system at Arizona.
Rocky Long used the 3-3-5 in two years as San Diego State's defensive coordinator and kept the scheme when he became the Aztecs' head coach in 2011.
The Louisiana-Monroe Warhawks have had success with it this year, beating Arkansas in Little Rock and playing close games against Auburn and Baylor.
Western Michigan also switched to the 3-3-5 this season, Arizona State coach Todd Graham has used it at times in his hybrid, multi-formation defense, and Wisconsin goes to it about 30 snaps per game.
``You can show people different looks,'' said Strong, now the head coach at Louisville. ``Because it's a balanced defense, they don't know where to attack you from and they don't know where you're attacking from.''
Unpredictability is part of the 3-3-5's appeal.
The defensive linemen in the 3-3-5 tend to be smaller and more mobile, their main objective not to rush up the field, but to tie up blockers so the linebackers and safeties can fill the gaps and make tackles.
The secondary typically features a pair of cornerbacks and a free safety with two other safeties - Arizona calls them spur and bandit - who are often hybrid strong safeties/outside linebackers who can stop the run, play the flats or cover tight ends in man coverage.
The point of it all is to make the defense difficult to decipher.
With so many skilled players lining up in a multitude of spots on the field, it can be hard for offensive players to keep track of their assignments, particularly on zone-blocking schemes and pass protection.
The 3-3-5 also allows for a seemingly unlimited number of blitz options, whether it's a linebacker on a stunt, safety up the middle or a cornerback charging in from the edge.
``That was kind of the whole intent of this thing when people started: Where are they going to bring their fourth or fifth guy from?'' Gibson said. ``Everybody in our defense, we have a blitz for them at some point, with the field corner being the exception. Everyone else could come.''
Part of what makes the 3-3-5 such a good fit against the spread is that adjustments from the sideline, whether in personnel or play-calling, are often quick and easy because there are so many athletic, interchangeable players on the field.
Where it can get into trouble is against power-running teams with big offensive lines that can push the smaller linemen of the 3-3-5 back.
If the linemen get knocked off their spots, the gaps, which are already bigger than usual because there are only three down linemen, can become larger or filled with 300-pound behemoths, which smaller linebackers and defensive backs certainly don't want to see.
The 3-3-5 also puts a lot of pressure on defensive players to think on their feet.
The defense is designed to allow athletic players to charge around the field and make plays, but it doesn't do any good if they're going fast without a purpose. The players have to know what their assignments are and the tendencies of the offense out of each formation or they'll end up getting burned for a big play.
``You have to be intelligent because even though it makes it hard on the offense, it's more complicated for us as a defense,'' Wisconsin linebacker Chris Borland said. ``You have to be keyed in to your assignments and your adjustments with what the offense shows.''
The defense isn't for everyone.
West Virginia ditched it when Casteel left for Arizona, Strong didn't take it with him to Louisville and Dunn, now coaching at McMurray, never turned it into a big-time success.
San Diego State gave up 90 combined points in losses to San Jose State and Fresno State, and Arizona has struggled defensively in Rodriguez's first season - 111th in total defense at 480.50 yards allowed per game - though that may have as much to do with the Wildcats' lack of depth as their scheme.
Still, the 3-3-5 can be effective when it's clicking, a novel approach that's tough to prepare for and keeps the opposition off-balance.
In an era when offenses have had the upper hand, anything that keeps teams guessing is worth trying.
AP Sports Writer Gary Graves in Louisville, Ky., and freelancer Benjamin Worgull in Madison, Wisc., contributed to this story.