The German was a surprise club-record £42 million deadline-day signing at the Emirates Stadium, notching four goals and a league-high seven assists since his arrival.
|20/1||Mesut Ozil is 20/1 with bet365 to score two or more goals v Chelsea|
"Mesut is a phenomenal player, one of these players that you buy to complete the puzzle of your team," Mourinho is quoted as saying by The Guardian.
"You don't need time with him, you need nothing. The player just arrives. His quality and his maturity and his leadership ... you put him in and you know automatically your team becomes better.
"There are many ways to improve your team. One of them is to work with young players and another is to go directly to the market and buy one of these finished products. Arsenal had the chance to do it with Mesut and they did very well.
"I think, in the deep of their souls, [Arsenal] think they can [win the title]. In my previous time here, Walcott was a kid. He's now a man. Other players are in the best moment of their careers - [Jack] Wilshere, Ramsey and [Kieran] Gibbs."
Mourinho - who missed out on No.1 target Wayne Rooney during the summer - was less positive about Chelsea, hinting that fans will have to wait until next season for the first piece of silverware of the Portuguese's second spell.
"Next season, Chelsea will have a phenomenal team," Mourinho said. "Between the work we are doing [on] the evolution of the players and a couple of clinical signings [next summer].
"When you buy two clinical players to complete the puzzle you are building, I think that Chelsea next season will have a really very good team."