The Spain international, who moved to United in a £37.1m deal in January 2014, hasn’t started a game since a 3-0 win against Cambridge United in the FA Cup on 3 February, making just three appearances from the bench in the Premier League.
Mata has been linked with a potential return to La Liga in recent months after failing down the pecking order at Old Trafford, with reigning Spanish champions Altetico Madrid thought to be interested in a move for United midfielder.
“I’m working in the same way I have always done, with the same attitude and the same passion! That´s all I can do, I’m always optimistic and ready to contribute to the team at any time!” Mata wrote during a question and answer session on Facebook.
The European championship winner has been a late substitute in United’s last three Premier League games, racking up a total of 23 minutes of top-flight action.
Mata won the FA Cup with Chelsea in 2012 after a 2-1 victory over Liverpool in the final at Wembley.
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