From SPurs pont of view they are selling Walker because he has been a bit of a bell end and is falling out with the manager see end of last season s selection . They are alos presumably keeping Alli, Kane, Loris, Alderweireld , Eriksson Rose & Vertonghen. Probably more important players to them than Walker(and I think he is a good player and am delighted we look to be signing him) furthermore they will get a much better fee for him than we did for Tevez.
I am not for a minute saying we shouldn't have sold Tevez but it is a matter of fact that even big clubs will sell one of their better players from time to time.
Walker is a good player and would improve any side
Spurs are selling him because he is disruptive, lazy, untrainable and stupid. And Pochettino won't tolerate that. However good a player he is.