United tried desperately to sign the 25-year-old centre-back after his impressive performances for England at the World Cup.
"Obviously going into a World Cup - if we were successful, as we were - there were always going to be players who came under interest. That is part and parcel of the game," Maguire said.
"I spoke with Leicester after a bit of interest from clubs, and they reiterated that I wasn't for sale and I respected that decision.
"They gave me an opportunity to play in the Premier League, when I had just been relegated with Hull. They gave me that opportunity and it is a club I am really enjoying my time at. I am playing week-in and week-out, which is important to me.
"They have given me the platform to play at the World Cup, so I feel I owe them and I respect that decision. Now I am looking forward to the season."