I'm not comfortable with losing him at all. Not only do I think that he will become one of the best in his positions, but I also think doubt that we would adequately replace him if sold.
I think a few factors have tilted his head; substantial interest from Barça (according to most in the Catalan press he's one if their top four priorities this summer), potential family issues (don't believe), Crystal Palace away, and missing out on CL.
Either way if we do sell him, which I'd be VERY reluctant to do, we should demand a high price. Let's see if Arsène and the board have changes