If you want to negotiate, it’s always important to “close the deal” when there is an opportunity to do so.
If you don’t you risk the possibility that you may lose the deal or receive less value than was initially on the table. There may be an element of this going on in the Fabregas transfer saga. If a deal drags on the other side can suffer buyer’s remorse, or come to value the asset they are negotiating for differently. Or economic factors may come to influence the other side’s thinking differently, or they may develop other deal priorities (Sanchez? Rossi?). Judging by the public statements coming from Barcelona it may be that they do now value the player differently than they did last year, when there was clearly an opportunity to close the deal which Arsenal rejected.
Of course last year Arsenal didn’t want to negotiate, but you have to think these stances through to the end. If a player really doesn’t want to stay at a club then that will be reflected in his performances, and arguably that happened with Fabregas last season. Now when it sounds like they might be prepared to consider a deal, Arsenal find that the ground has shifted and it may not be so easy to close the deal at a price that they want. Closure is a fluid moment – it’s generally best to bottle that moment and get the best deal done whilst you can.