Manchester United agreed a club-record transfer to bring Juan Mata to Old Trafford from Chelsea on January 24, 2014.
The Spanish midfielder had fallen down the pecking order after two-and-a-half years at Stamford Bridge despite being player of the year twice and was allowed to depart to a major rival.
The transfer fee of £37.1million was more than £6million higher than the previous record United paid for Dimitar Berbatov six years previously.
Speaking about the move, then Chelsea boss Jose Mourinho said: "It's what he wants.
"It's what he asked us to accept. Chelsea Football Club is proud to act this way, in an open way, in a human way. The offer, compared with what the club paid two years ago, was fantastic.
"We hope he does well. We are convinced he is going to do well. If Manchester United pay their record for a player it's because they know exactly what they want. They are convinced he's going to be important for them.
"In spite of probably many clubs, many boards and many managers think you can't sell a top player to a rival club, especially not in the same country you play, we feel and we think differently.
"The player deserves respect, the player deserves to be happy and to play where he wants to play."
Mata's move was completed the next day and was seen as a crucial moment for embattled manager David Moyes but the Scot was sacked three months later.
Mata's stay at Old Trafford has proved much more enduring, with the Spaniard having made more then 250 appearances in all competitions under four different managers, including Mourinho, and scoring 50 goals.
