Mata is poised to play at the home of his former employers for the first time since his shock £37.1 million transfer to Old Trafford in January 2014.
The Spaniard failed to get the first-team opportunities he craved under Mourinho, who insists everyone at Stamford Bridge - namely the coaching staff and the players - still has the utmost respect for a player who gave so much for the west London outfit during his two-and-a-half-years there.
Mourinho: We are happy Mata is doing well
“He's a player with a history in this club,” Mourinho was quoted as saying by the London Evening Standard. “Every player in this club has deep respect for him as a player, as does the manager.
“We all wished him the best when he left. We are all happy with him: a very correct boy, total professional. We're happy things are going well with him.”
Mata failed to convince Mourinho
Mata was often overlooked by Mourinho, despite the fact he has secured Chelsea’s Player of the Year award in both of his two full seasons at Stamford Bridge.
The 26-year-old has experienced difficult moments at Old Trafford under Louis van Gaal, too, but appears to have finally convinced the veteran Dutch coach that he deserves to play every week.
Mata has scored three goals in his previous three Premier League matches - two against Liverpool and one against Manchester City - and will be desperate to continue his impressive goalscoring run by netting his ninth goal of the season against Chelsea.
Mata is a better playmaker than Oscar
Some Chelsea fans felt at the time Mourinho should have kept Mata over Oscar; 15 months down the line and it’s not difficult to see why.
Was Jose Mourinho right to sell Juan Mata to Manchester United in January 2014? Have your say by leaving a comment in the box below!