Graham Potter says he felt he had to "grasp a new opportunity" as he explained in an open letter to fans why he left Brighton to join Chelsea.
"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."
Potter, who has replaced the sacked Thomas Tuchel at Stamford Bridge, added: "I hope that you will understand that at this stage of my career, I felt I had to grasp a new opportunity.