The Spaniard traded Stamford Bridge for Old Trafford in 2014, joining in a deal worth £37.1 million.
For the Red Devils he made 285 appearances and scored 51 goals.
He also helped the club to an FA Cup triumph in 2016 and a Europa League – League Cup double a season later.
Despite the tough times that have plagued United throughout much of his spell there – Mata has been a fan favourite for many and his presence will be sorely missed.
The feelings mutual, though, because Mata has proven time and time again his love for United – not just through his work ethic on the pitch, but through standing up for the club as well.
Video: Mata stands up to Sterling
In the Manchester derby of November 2018, United travelled to the Etihad for a tough away encounter with their city rivals.
City were embroiled in a bitter title scrap with Liverpool for the Premier League and the Red Devils knew they would be up against it prior to kick-off.
Unsurprisingly, City were winning the match 3-1 in the last seconds and were passively knocking the ball around looking to run down the clock and see out the victory.
When the ball came to Raheem Sterling, the Englishman started sarcastically performing step-overs to take the mickey out of the United players before heading for the corner.
Mata was infuriated and charged over to Sterling after he was tackled to give him a piece of his mind.
What did Mata say? What was Guardiola’s reaction?
When quizzed about the incident by The Times, per Football365, Sterling said that Mata ran up to him and told him to: “Show a bit of respect.”
Pep Guardiola had similar thoughts, saying after the game: “I like a lot the way [Sterling] played,” said Guardiola, who appeared to voice his displeasure with his player on the pitch at full-time.
“The best way is to keep the ball and he did it with Leroy and Phil. In that situation with two or three minutes left to go, they controlled it absolutely. It is better than just defending.
“But [Sterling] made some movements with the legs that we can avoid. But he’s young and he is going to improve.”
Sterling rebuffed the claims that he was showboating and instead suggested it was tactical piece of play to draw the foul.
“I was keeping the ball in the corner.” Sterling said, per Football365
“I can understand if we had lost the ball, and they’d gone down the other end, but I am trying to waste time, attract a foul.
“I wasn’t trying to disrespect them. I wouldn’t. I was just trying to keep the ball in the corner and entertain the fans at the same time.”
Whatever the reason, Sterling’s showboating certainly proved a great platform for Mata to firmly place himself in the hearts of United fans forever.
Thanks for everything, Juan.