The Argentine winger joined the French champions on Thursday just 12 months after his much arrival at Old Trafford from Real Madrid.
Di Maria, who cost United a record £60m, failed to settle in Manchester and made just 33 appearances for the club, scoring just 4 goals.
And he has apologised for his failure to make things work at the Premier League club.
“I write this note to thank all the Manchester United family for the great support received during the year I’ve been part of this club,” wrote Di Maria.
“I can guarantee you it was not for trying. I did my best but football is not like maths: often a lot of things out of our control affect the way we feel and the way things turn out. I am sorry it did not work out as I would have wished in this amazing huge club.
“I want to give special thanks to all the directors and management of Manchester United as well as to every member of the staff and colleagues as they gave me all their support. Also a special mention to all the fans who always trusted me and showed me their respect and love.