It's ludicrous to even consider Duff over Jonas.
It would be if you were dropping Jonas for Duff aye.
Fair enough then I thought you were suggesting that but still Jonas is a winger, converting him to a defensive midfielder isn't the answer IMO, just because he can run a lot and and gets stuck in doesn't mean he'd be good in that role, in fact you're limiting him as a player if you take his ability to dribble with the ball and try and beat men because that's the best bit about his play.