Graham Potter says he had to "grasp a new opportunity" as he explained why he left Brighton in an open letter to the club's supporters.
Potter was appointed Chelsea head coach on Thursday after three years at Brighton who he took to ninth in the Premier League table last season - the highest league position in the club's history.
After six matches of the 2022-23 Premier League season, the former Ostersunds and Swansea manager led Brighton to fourth after four wins and one draw.
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Now after signing a five-year contract to manage Chelsea last week, the Englishman has thanked the Brighton fans for supporting him.
"For some, I recognise that the change that comes so suddenly in football can be hard to accept," he wrote.
"I may not be able to persuade you all to forgive my departure - but I would at least like to take the chance to say thank you."
He added: "I hope that you will understand that at this stage of my career, I felt I had to grasp a new opportunity."
Potter says he believes he is a "better manager" following his time at Brighton.
He continued: "I feel I am a better person and a better manager for the experiences I have had here. Not every team selection or decision has been perfect. But the club has created an environment that gives you the scope to make mistakes, learn from them and then improve.
"I have always tried to act with integrity and be a good person. These are values I hold dear, and I know that the Albion do too."
Chelsea's former boss Thomas Tuchel was sacked last Wednesday with Potter appointed the next day. Potter said the events that unfolded last week were an "unexpected whirlwind".
He said: "What turned out to be my final match against Leicester City last Sunday [a 5-2 win] was a good way to end. I did not know at the time that it would be the end, but looking back now we played so well.
"There was so much positivity around the club. The last few days have been an unexpected whirlwind."
Potter's first game in charge of Chelsea is scheduled to be against RB Salzburg in Champions League Group E on Wednesday.
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