The 31-year-old decided to go against the will of then-manager Sir Alex Ferguson by seeking pastures new, departing for the second tier and eventually working his way back to the top.
Heaton spent time with Cardiff City and Bristol City before landing a move to Burnley in 2013, where he played a big part in the Clarets' two promotions to the top flight and was rewarded with a couple of caps for England.
Speaking ahead of Burnley's meeting with United on Sunday, Heaton told Sky Sports News: "I always felt I needed to go and earn the stripes really. I always felt I was going to be good enough, I just wanted to go and get the experience, the practical experience, and at that point I didn't have it.
"That was probably the best decision I made. It was my decision. I stand by the decision, it was a tough one to make, with it being Manchester United having signed there as an 11-year-old."
Heaton has made 30 appearances for Burnley in the Premier League this season, keeping a total of nine clean sheets - the same number he managed two years ago across 38 outings.