He is a great fan of the German midfield star and the pair keep in touch after their time together at Real Madrid.
Mourinho said: "He's a phenomenal player. He's one of those players that you buy to complete the jigsaw when you build your team.
"There are players who you buy and you know it will require work to mould them to your style and to get the best out of them.
"But Ozil needs nothing. He arrived, Arsene gave him the shirt and he immediately started playing and immediately the team became better. He is a phenomenal player."
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