Loosing Vidal from a sporting perspective is pretty bad, but it's not catastrophic to be honest. We do have a depth, and what not, and we tactically very flexible, not to mention we've managed to play two thirds of the season with a sub par Vidal and still made shit happen.
The real damage is behind the scenes. We are damaging our reputation as a club if we are selling Vidal at such a mediocre price and nothing in return. If we were to miraculously get Gotze in exchange, that would make a huge statement to the rest of the clubs out there and to our own players. We are trying to move up, even though it's not guaranteed that Gotze would be half as successful as Vidal. We are gaining a player that would be welcomed to almost every big club out there, in exchange for another coveted player. However getting what is literally considered chump change in today's market for a player that is wanted by literally every big club, is basically like telling the world we ain't shit. Big clubs are not big just because of their trophy cabinets, how they conduct their business is also a major factor, and we are doing business the same way that Udinese is (buyback clauses, undervaluing our assets), for fuck sakes Porto is a bigger club than Juventus in that sense, they get what they ask for, and have the balls to ask for something big in exchange of something that they have.