Why would Minnesota trade one of their best forwards for 3rd liners?

Ferland has filed for Arbitration, so the most he can get in contract term is either 1 or 2 yrs.

That's only if it goes all the way through the hearing and the arbitrators hand down a decision; which is very unlikely to happen. He can sign whatever contract (term and money) he likes before that.

Wild "should" have enough to sign the rest of their roster.

No - they still have serious cap issues. They only have 8 forwards under contract, and 6 defensemen, including Ryan Murphy who many are saying is not NHL quality.

Granlund at $6.5 (many are saying he is due more than that, closer to $8), Nino at $5.0, which may be slightly low, and Foligno at $2.5 (last year he made $2.25 also has earned a raise and that is not much of one). That is $14 million of the $16.4 available. They are at 11 forwards.

With $2.4 available (and that is if all the signings go well), even if they leave Murphy on the roster, they need to sign or promote 4 players. That breaks down to $600,000 per player. If even one of the 4 makes more than $600,000 then they can't make cap. I left Svedberg at $700,000 in goal. If Granlund signs for $7 to $7,5 and Nino gets the $5.5 everyone says he is due, they will need 4 players to fill the roster with only $900,000 to $1.4 of cap available.

Next year may be even worse. Koivu's contract comes to an end, but Zucker, Dumba, and a backup will all need raises. They will still have a Dman problem with only 4 under contract if they sign Dumba.