The centre-back was once a youth player with the Red Devils, who were eager to recruit him from Burnley, but he opted for the Toffees instead.
“They were in touch with my agent and showed a lot of interest,” Keane told The Times about United’s pursuit.
“They wanted me, but a few things happened and I thought Everton would be the best place for me to come.
“I thought I would get a lot of game time here, more than I possibly would at Manchester United, and that was a massive factor in my decision.”
Keane will not be letting sentiment get in the way during Sunday’s clash between the clubs at Old Trafford, revealing that his years with the Clarets had blunted his affection for United.
“To be honest, having been at Burnley for three years, I wasn’t a fan of the club like I used to be,” he added.
“I wasn’t as big a fan of Man United as I had been, so I had to sort of put that to one side and just think rationally about what would be best for me as a footballer.
“My family are all Man United fans so it was not an easy decision. My dad would have been delighted if I had signed for United. But he is glad I have come to Everton and not Liverpool, put it that way.”