How long the contract is, isn't relevant when talking about current salary. It's definitely a burden that we have Vidal who's making 6m€ net while giving these penalt...performances. Like it's a burden (even bigger) that we have Eriksen who's making 7.5m€ net while not even playing.
It's the opportunity cost. We pay Vidal a lot and he doesn't play according to the money we pay to him. We could be paying that money to someone else. Or to somewheree else (transfer fee to another club + lesser salary to a player). These veteran signings of Vidal and Kolarov have been really disastrous. Only silver lining is we didn't pay anything to get Vidal (apart from the 1m€ fee if we win a trophy). If Vidal doesn't pick up his game, it just looks bad, bad signing no matter how you look at it.