The Portuguese boss will leave Real Madrid at the end of the season and is widely expected to return to Stamford Bridge for a second spell as Chelsea boss.
"Jose is one of the best," World Cup and Euro 2012 winner Mata told reporters on Chelsea's United States post-season tour.
"He won everything in every country he was - in Portugal, in Italy, in Chelsea in London.
"We don't know really what is going to happen but if he comes he is welcome because he is one of the best and Chelsea always want to be a top side.
"If he comes we are going to be happy to have him."
- Sports & Recreation