Khedira knows the German playmaker well from their time together with both Real Madrid and the national team so is well-versed to make a judgement call on the 24-year old who he describes as a 'genius'.
"Arsenal had a strong team anyway, but Mesut makes them the best team in England," Khedira said.
"I am sure he can be the player that makes things happen for them and win them the championship. Mesut is a genius on the field, there is no other way to describe him."
He added: "Of course there was some disappointment among the players at Madrid because he is the best in his position in the world.
"But I understand his decision as a player and also as my friend. He is already playing amazing football for Arsenal and he hasn't even got used to the Premier League yet."
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