The biggest need left as the Vikings maneuver through Week 2 of free agency while preparing for the draft is linebacker.

Beyond Chad Greenway, the Vikings have no proven starting-caliber players to fill the other two spots in a 4-3 scheme. But there are several factors that have kept the Vikings from scratching that itch the way they've gone out and addressed needs at quarterback, defensive end, nose tackle, cornerback, left guard and depth at receiver.

Let us count those factors:

1, The free agent market at linebacker is weak and/or aging.

2, The Vikings have seven linebackers under contract. Three of them – Audie Cole, Michael Mauti and Gerald Hodges – are young players the Vikings are high on. A fourth one – Jasper Brinkley – was re-signed before the start of free agency because the new coaching staff thinks he might be good enough to compete for a starting job or provide depth. Brinkley was a bust in Arizona last year, but given a limited role, he can be an acceptable downhill run-stopper.

3, The Vikings are looking for a difference-maker, a playmaker, a young guy with speed and instincts and a physical presence. The place you find those are relatively high in the draft, not on the street.

4, The Vikings are changing their defensive scheme under new coach Mike Zimmer. The staff is still figuring out how the different skill levels will match the new roles. And that includes Greenway, whose role for years has been a strong-side backer whose primary responsibilities were in coverage.

Here's what General Manager Rick Spielman had to say about the linebackers when I asked specifically about the weak-side position, which appears to have Hodges, an unproven second-year player, atop the depth chart:

"I wish you could say you had 22 guys that you're going to line up with and say that they're all proven starters," Spielman said. "That's not the way the NFL is. You have to play these young guys and you have to get them ready to play and we have an unbelievable coaching staff that I know will do a great job of getting these guys ready to go.

"When you look at Audie Cole, he did a nice job when he came in at Mike [middle linebacker], he can also play the strong side. Hodges can cross-train because the strong side and the weak side. They're talking about doing some things with Chad Greenway, and Jasper Brinkley can play some Mike and he can play some strong side.

"I think all of that stuff will sort itself out once these guys get on the field and once we get through the draft and figure out what the best combination is for these guys. All of these guy, we feel that they do have ability, most of them are able to cross-train between one linebacker position and another.

"It's a different philosophy on the linebackers as far as what Coach Zimmer is going to use in the nickel situations and the dime situations that is a little different than what we've had here in the past. I'm excited to see how all of that comes out."

Asked if the coaches were looking at moving Greenway to middle linebacker, Spielman said:

"I don't know. That's the coaches' decision. I know he's played on the weak side, he's been in our nickel package and stuff. Like I said, they do a lot of things from a defensive side that's a little different from what we've done in the past and once these coaches figure out what the skillsets are and once they get an opportunity to put their hands on these players to figure out what their best skillset there, they'll figure out how to best utilize them on the field."

In other news today …

. The Vikings confirmed the visit of offensive lineman Vladimir Ducasse earlier today. Ducasse, a 6-5, 325-pound guard, previously visited Cincinnati. A second-round pick of the Jets in 2010, Ducasse never lived up to expectations. He has started only five games, four of them coming last season. Ducase leaving town without a deal isn't a surprise. The urgency to sign him was lessened over the weekend when the team agreed to a two-year deal to bring back starting left guard Charlie Johnson.

. Bears defensive tackle Henry Melton, who visited Winter Park last week, continues his tour of NFL teams. He reportedly left Dallas last night and is scheduled to visit with the Rams today.

. Overthecap.com reports that receiver Jerome Simpson signed for $1 million, including a $50,000 roster bonus and a $50,000 workout bonus. The site also has the Vikings $15.3 million under the salary cap, but that does not factor in guard Charlie Johnson's recent deal.

. Zimmer is among the coaches at Florida State's Pro Day today.