It is often brought up about the players that Jose Mourinho allowed to fall by the wayside at Chelsea.
Kevin De Bruyne, Mohamed Salah and Romelu Lukaku are the names are often named as those who Blues fans will always regret losing.
However, one player who stands out almost above all others is Juan Mata.
The talented left-footed maestro came into the side from Valencia in the summer of 2011 and made an immediate impact.
Chelsea had one of the most creative number 10s in the Premier League, and week in, week out he performed to a top level.
In his first Premier League season he made 13 assists, while he backed that up in his second campaign he got another 12 assists, this time with 12 goals.
Of course, Mata played a huge part of that historic Champions League victory in 2012, whipping in the corner for Didier Drogba to nod home.
A year later, the Spaniard was the man who provided the ball from another corner on to the head of Branislav Ivanovic for the Europa League final winner.
Mata's fine performances did not go unnoticed by the Chelsea supporters, and he was named Player of the Year for both of his seasons with the club.
So going into the 2013/14 campaign, expectation was high on what Mata could produce once more at Stamford Bridge, while Jose Mourinho returned to west London to replace interim boss Rafa Benitez.
However, the excitement came to nothing when the Spaniard was unceremoniously dumped on to the sidelines, with Oscar becoming the go-to man.
It was a strange moment, see a player who had inspired Chelsea to two European titles being left in the lurch and without a secure future.
Come January 2014 and the transfer window, Mata was seen as surplus to requirements and sold to Manchester United for a little over £37million.
"I have no personal bitterness towards him at all," Mata told the Mail. "My football is not perfect for his idea of football. That’s what happens.
"I was at Chelsea, player of the year for two years, everything was rosy and then he arrived with a different approach, which I respect because there is not only one approach in football."
But or Chelsea fans, the fact that Mata was sold in his prime to a direct rival was a bitter pill to swallow.
Now, at the age of 31, Mata plays a bit-part role in United's team under Ole Gunnar Solskjaer, but still has the ability to cut through a defence with a pass when needed.
In his prime, one of the most naturally gifted players the Blues have had. And it stings he moved on the way he did.
