The midfielder was a rising star at the Blues where he made his debut in May 2015, but a series of injuries has forced him to say goodbye to the game.
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Brown was most recently at Preston North End, but suffered a ruptured Achilles in pre-season just under a month after he signed in 2021.
He was released towards the end of the season, and has now hung up his boots with an emotional farewell on social media.
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Brown tweeted: "I really don't know where to start, although I always thought I'd have to write this one day, I just didn't think this day would come so soon.
"It is with great sadness and a heavy heart that after a long year of struggling from two Achilles tendon surgeries, I now have to retire from professional football.
"As soon as I could walk, I always had a football at my feet. That was me, that was my happy place. I lived a dream that most don't get the opportunity to live and for that I will always be eternally grateful.
"To get to play the sport I love brought many happy times during my life. It also delivered many challenges that I wouldn't have been able to get through without the love and support of my family and friends.
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"The sacrifices my mum and grandad made for me from the age of four-years-old, gave me the chance to live a life I always inspired to live.
"Driving from Peterborough to West Brom 3/4 times a week after school, just to get me to training and matches, I'll forever be grateful.
"I think my Mum only missed one match in my whole life. That just goes to show how much you can really achieve with the love and support from the people closest to you.
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"I will always remember the memories I have made. They will live with me forever. From being told I was going to be on the bench against Chelsea, to making my debut against Wigan at the age of 16 for West Brom.
"Then getting to make my debut for Chelsea, the club I dreamed of playing for when I was a little boy!
"And I'll never forget getting promoted to the Premier League with Huddersfield at Wembley. That will forever be one of the happiest and greatest moments of my life.
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"Football doesn't define me as a person. I'm a father, a son, a brother and a friend, and I will still be that after football. I've lived my dream and memories that will stay with me forever.
"To every club that I have played for, I really appreciate you all for believing in me and giving me a chance to play the game I love.
"Lastly, I just want to say thank you to all the fans that have supported me and sang my name, there is no greater feeling than hearing that.
"You mean the world to me, and always will. I wish you all nothing but happiness and love. Take care. IJB."
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Chelsea replied to his post, as they said: "All the best for the future Izzy."
Former Chelsea boss Jose Mourinho had high hopes for Brown's England prospects, saying in 2014: "My conscience tells me that if, for example, [Lewis] Baker, Brown, and [Dominic] Solanke are not national team players in a few years, I should blame myself.
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"They are part of a process the club started without me. In this moment, we have players who will be Chelsea players. And when they become Chelsea players, they will become England players, almost for sure.
"At 16 or 17 I don't think it's good for them to go somewhere else to play, like in the Championship. At 17 they have to train with us and they have to learn with us. They will learn a lot."
Brown signed for Chelsea from West Brom in 2013, but made just one appearance for the Blues during his eight years at the club.
Most of his time at the west London giants was spent out on loan, featuring for Dutch outfit Vitesse, while representing Rotherham, Huddersfield, Brighton, Leeds, Luton and Sheffield Wednesday in England.
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Brown left Chelsea permanently for Preston in 2021, with his previous seasons also being blighted by ACL and hamstring injuries.
He played in a total of 133 games during his career - chipping in with ten goals and assisting another 16 across all competitions.