The 30-year-old came through the Red Devils academy and was at the club for 15 years before signing for Everton.
"The hard part for me though was the year under [David] Moyes. The way the fans turned on you.
"That was my club you know. I had been there since I was 11-years-old. For the fans to go as sour as they did.
"That disappointed me. I was a player who would try 100 per cent a game. It wasn't fact of trying I just wasn't good enough that year.
"That was the thing that disappointed me but the actual leaving I didn't have a problem with, no."