Published Wednesday, 02 November 2011
McIlroy jumped ship from Chandler's International Sports Management company just ahead of the Shanghai Masters, where he went on to win the biggest prize in sport - a cool £1.25m.
But the Holywood star insists there was "nothing personal at all" behind the move.
"I thought long and hard about it and had a lot of chats with my Mum and Dad. Sometimes to go forward in your career, you just need to make decisions," McIlroy told BBC's 5 Live.
Just like to say we had a great 4 years and life moves on, for both of us.
Andrew Chandler on Twitter (@chubby6665)
"For four years, I felt Chubby was the best guy and ISM were fantastic for me - but sometimes to progress you need to have a fresh view on things.
"It's about me trying to play my best golf and that's all there is to it.
"I feel like a new environment around me ... it might enable me to play even better and I feel like I'm moving on to the next stage of my career."
And the 22-year-old remains full of praise for his former manager and the man he says was "there for me since day one".
McIlroy added: "I remain very close to him - it was a purely business decision and nothing personal at all. I've got all the time in the world for Chubby and everyone involved at ISM."
In quitting ISM, Northern Ireland's US Open champion walked out of the stable which had four of the last six major winners, plus world number two Lee Westwood.
He joined Dublin-based Horizon, who also represent Portrush's Graeme McDowell.