INDIANAPOLIS – The beauty of the 3-4 defense, according to Vance Joseph, is the element of surprise.

Five or more players position themselves near the line of scrimmage, which creates a guessing game for pass protectors.

"Who's the fourth rusher?" said Joseph, the Cardinals' new defensive coordinator. "That's what offenses don't like. … You're not just giving them a way out when they break the huddle – there are the four down (linemen), we're blocking those four. Now when you break the huddle, you've got double press corners and you've got five guys down. Now you have to solve some problems."

The outside linebackers are the key to the scheme. First and foremost, they must be able to get after the quarterback. If they can cover, too, it opens up an array of blitz packages.

That type of versatility is rare, and it's why Kentucky outside linebacker Josh Allen finds himself rated among the top prospects in the draft. He had a phenomenal senior season, compiling 88 tackles, 17 sacks and five forced fumbles, and throughout his career showed the ability to defend the pass.

"Josh Allen, what makes him special is not only what he can do rushing but what he can do in coverage," NFL Network analyst Daniel Jeremiah said. "So many teams (have) these athletic tight ends. I'd like to see him rush, but you can deploy him in coverage and he holds up just fine."

Allen draws an easy comparison to Cardinals outside linebacker Chandler Jones. They are both 6-foot-5 and about 265 pounds with rare bend that makes them elite pass-rushers. Allen believes his talent likewise matches up to another pair of Pro Bowl edge-rushers: Khalil Mack and Von Miller.

"They're both the best at the position and I feel I'm the best, so I feel I should compare myself to the best," Allen said. "I feel my game symbolizes both of theirs."

The Cardinals have a critical choice to make with the No. 1 overall pick, and Allen would love to be in that mix. Draftniks often list him alongside Ohio State defensive end Nick Bosa and Alabama defensive tackle Quinnen Williams as the three best defensive prospects, although Jeremiah has him behind them in his rankings.

"The reason I don't put him up there with the other two – I think the other are two are better two-way players against the run," Jeremiah said. "With him, he's a little bit light there. He looks beautiful but there are times when he kind of gets moved around."

Jeremiah noted that the order of the top three could depend on a team's preference, and it seems like Allen's skillset would fit Joseph's vision perfectly. It's easy to imagine Allen feigning a pass-rush to occupy an offensive tackle before dropping into coverage while Haason Reddick shoots the 'A' gap.

"If a team wants me to drop, I'll drop," Allen said. "If a team wants me to rush, I'll rush. If a team wants me to do half, I'll do that."

It's unknown where Allen will land in the Cardinals' rankings, but even if he's not No. 1, that doesn't eliminate a possible pairing. General Manager Steve Keim said he is open to trading down if the circumstances are right.

"It goes back to trusting your board," Keim said. "If there are five players you think are Pro Bowl-type talents that fit what you do and are going to be good in your locker room, you'll feel comfortable with moving back 'X' number of spots if you're acquiring a lot of value."