As the Portuguese continues to be heavily linked with a return to Stamford Bridge, Spain international Mata has spoken out about his love for successful jobs the Real Madrid boss has done throughout his career.
"Talking about Jose, for sure he's a great manager," he told Sky Sports News.
"I mean, he won everything almost in every country. He was in Italy, in Portugal, here in England, and I think the players we have now for example in the dressing room have very good memories about him.
"And in Madrid I think the same. He's done a good job, Real Madrid is one of the best teams in the world, he is one of the best managers.
"We don't really know what is going to happen but, for sure - and that's a fact - he is one of the best managers in the world."