United go to Mata’s former club this weekend.
Mata wrote for his blog: “We travel to Stamford Bridge – a place that’s been very important in my career, as you know.
“That was a few years ago, but my gratitude to all the people at Chelsea for what we had there is still present. Beyond that, playing against the current Premier League champions is a true challenge, one of the toughest games of the season, and we want to show what we are capable of and get the three points.
“Millions of fans around the world are looking forward to this game. It’s one of the biggest days in the Premier League calendar.”