By Jack Gaughan PUBLISHED: 07:22 EST, 26 January 2014 | UPDATED: 03:10 EST, 27 January 2014 Will Juan Mata be a success at Man United? Juan Mata has told Chelsea fans he had planned to stay at the club for the rest of his career in an emotional letter, admitting frustration at a 'complicated' six months was the main reason behind leaving the club. The Spaniard completed a £37.1million deal to join Premier League rivals Manchester United on Saturday. But he couldn't move to Old Trafford without saying goodbye to Blues fans - revealing that he had to open a new chapter for the good of his career.
@highlight
Juan Mata writes to Chelsea fans thanking them for their support
@highlight
Midfielder reveals he was ready to stay at the club for a 'long time'
@highlight
Spaniard completed £37.1m move to Manchester United
@highlight
Mata wrote that he had 'difficult experiences' under Mourinho
@highlight
Playmaker said it is 'a day of mixed feelings'
Blessing: Jose Mourinho said the club had to be 'respectful' of Mata for his move to @placeholder