I think it'd be a huge mistake to let Tadic go personally. Very creative player and a different option to everyone else in the squad. You can point to stats all you want for this season, but he was injured for quite a while, has been in and out of the team due to that and formation/rotation and has played with a team who on the whole underperformed for a long stretch.
Remember the stat about him crossing the ball more times than anyone else in the prem - and for most of the season Pelle has been on the end of those crosses and off form. Put Long up front all season, who is a much much better header of the ball, and you'll have seen a much better success rate.