Jose Mourinho believes the Arsenal side Chelsea are about to face are far more dangerous than the Gunners of old – especially now they have Mesut Ozil.

The Blues' boss knows all too well what to expect from Ozil, having worked with the German midfielder at Real Madrid and admits Arsenal's most expensive signing has added a new dimension to their play.

“He’s a phenomenal player and he’s one of these players that you buy and you complete the puzzle of your team and you don’t need time. You need nothing,” Mourinho said.

“The player arrives and you have an empty space waiting for them with his quality, maturity and leadership. The space is there and you put the player there and you know that automatically your team becomes better.

“There are players that you buy that you know now I need to work, adapt and find the best solution to get the best out of them and they need time to adapt.

"But he arrived, Arsene gave him the shirt, and immediately he starts playing and the team becomes better.”

In a show of respect that would never have manifested itself last time Mourinho was boss at Chelsea, the Portuguese admitted his old foe had created a side to be admired.

"To arrive at Christmas time top of the league, I think is a sign they’re fighting for the title," Mourinho said.

“He [Wenger]improved his team.

"There are many ways to improve your team. One of the ways is to work young people and give them time to grow up and improve. Another way is to go directly to the market and to buy one of these end product players in the top moment of their careers.

“They have a chance to do it with Mesut and they did it very well. He bought an important player that changes his team clearly.

"In my time here Walcott was a kid, he’s now a man. These other guys are players in the best moment of their careers. Wilshere and Ramsey and Walcott, Gibbs and these guys. They are in the perfect age.

"I’m not saying that Mesut transformed the team completely. The manager and the club gave these players conditions and time to have a great stability in their evolution.

"When you come and buy Giroud and Ozil and some other players, the team becomes much better and ready to do what they’re doing.”