Having to say goodbye to your boyhood club is always heart-wrenching. Constantly underrated, repeatedly made a fuss about, it's not until you're set to depart that you realize what exactly you're leaving.  

A product of the famed Chelsea academy, Mason Mount joined the English powerhouse at the age of six and went on to make 195 appearances for the Blues since his first-team debut in 2017.  

As the years passed, Mount established himself as a key player and fan favorite in Frank Lampard's first spell at Stamford Bridge, winning the Champions League, FIFA Club World Cup and UEFA Super Cup along the way.

But then the time comes to move on to pastures new. With a year left to run on his current deal, Mount knows only too well some Chelsea fans will not be pleased with his departure after 18 years at the club. However, as talks over extending his stay failed to yield a positive conclusion, a move to Manchester United is a foregone conclusion.

On Tuesday, the 24-year-old midfielder finally posted a farewell message to Blues supporters on Instagram, confirming their worst fears. 

"Given the speculation over the last six months, this may not come as a surprise to you, but it doesn't make it any easier to tell that I've made the decision to leave Chelsea," said Mount in a video message. 

"I feel you deserve more than just a written statement, so I wanted to tell you directly how grateful I've been for all of your support over the last 18 years. I know some of you won't be happy with my decision, but it's what's right for me at this moment in my career. 

"We've been through a lot together. Winning the Youth Cup, my Player of the Year awards, the Super Cup, the Club World Cup and of course that unforgettable night when we won the Champions League. 

"I want to say thank you to the academy, Jim [Fraser] and Neil [Bath] for being so influential to me from such a young age. The managers I've worked under, Frank [Lampard], Thomas [Tuchel] and Graham [Potter], the backroom staff, the unsung heroes of Cobham, all of my teammates over the years that have become my brothers. 

"My family for the continuous love and support and most importantly you guys for sticking with me throughout. Wish you all the best."

According to multiple media outlets, United have offered Mount a five-year contract with an extra year option. The deal is an initial payment of 55 million pounds ($69.9 million) plus 5 million pounds in performance-related add-ons, which are strongly dependent on appearances and success.  

Mount will be Erik ten Hag's first signing of the summer as the United manager looks to strengthen his squad following his team's qualification for next season's Champions League. 

It remains to be seen how Mount will slot into United's midfield. The English star could provide the intelligent movement, set-piece delivery and work-rate in both attack and defense while improving their quick transitions when out of possession. 

"I think Mason Mount is a very good signing, he will be a valuable member of the squad," United legend Rio Ferdinand told reporters. "He's a top player, I love the way he plays football. 

"Every manager he's had has been nothing but positive about him, integral to everything they do. He brings goals, assists, chances created, runs deep into the box, always a goal threat, decisive player in the team, he has to play. In big games, he can perform and impact games. 

"He's a high-intensity player, everything you'd want from an attacking player in midfield. For that price in today's market, he could turn out to be a very good piece of business."