Nemanja Matic was a Chelsea player for three seasons (in his second stint at the club) and won two Premier League titles with the Blues.
The Serbian moved to Manchester United this summer and will return to his old stomping ground on Sunday evening, as Chelsea play host to Manchester United.
Chelsea boss Antonio Conte has told his players to forget all the familiarity in this fixture until after the end of the game.
“I think in this time, you see only opponents. An opponent,” Conte said.
“I think this is the right way.
“It will be the same for Matic in the other side. I think he doesn’t care, he doesn’t care. The most important is to play for your place, to play for your club, to play for your fans. This is the most important thing now.”