Hart has no time for the goalkeepers' union when it comes down to the business of winning a derby.
He said: "What United do has nothing to do with me. When Edwin van der Sar retired he left big shoes to fill and although I might sound selfish and rude, I'm not interested in what's happening over there.
"Luckily he chose to go with me, but that's gone now and I don't think about it. As a goalkeeper you are either in or out. At one point I was out and Shay was in, so I went to Birmingham on loan.
"When I came back I was in the team and I love this club and love being here. Shay is a great keeper and a great person. I still speak to him because I look up to the guy massively. But luckily I got the chance to play for City and I am so focused that I don't care about how things are going for the United keepers."