Özil, albeit being world class, is not the kind of player who will lead a team and make it perform. There are a lot of attributes that he´s missing for that to work, mainly he´s rather an introvert and, in a set up that isn´t working perfectly, he will be missing more often than not. He´s probably the best in the world in making his team mates look better and if you put him in a functioning modern system like at Bayern, Barca, Real (who would have thought) and Germany (yes, despite the constant criticism of him in the english media, he was very good for us during the Qualifications and the WC. In England its unfortunately all about passion and athleticism and "WIM", the so called experts don´t care about the important, but not so obvious, little things). and give him a freeroaming role he will strive. Arsenal could very well be a team like this, but they unfortunately are really unbalanced at the moment and you get to see the bad side of Mesut to often.

Di Maria on the other hand is not as good as the average fan thinks he is. Why do you think Real let him go? Most of the fans (level 1 thinkers) thought he was one of their best players, because with his pace and one on one situations he delivered some highlights, but not Carlo. He´s way to wastefull in possession, inconsistent, average at passing/crossing and his decision making is not very inteligent, so of course he couldn´t stay in their midfield. In his natural position, on the wings, they have way better players too. Naturally they never would have stated that openly, because if they did, nobody would have overpaid for him like Woody did.

Players like Ronaldo, Benzema, Ramos, etc. making a big fuss when they let Özil leave, but, in contrast to some fans, couldn´t be more indifferent about Di Maria, should really tell you everything about their respective standing and abilities.