Foster is set to complete his move from Manchester United to St Andrew's for a fee that could rise to £6million.
Hart admits he wanted to stay at Birmingham but has been recalled by his parent club Manchester City after a successful season-long loan with Alex McLeish's side.
Return: Hart goes back to Eastlands
New start: Foster to join Birmingham
But he has no doubts that Foster, starved of first-team opportunities at Old Trafford, will be an ideal replacement.
Hart said: 'I think Ben will do it easily (follow me). He is a fantastic keeper.
'Ben has had some harsh criticism at Manchester United this season but, if he does turn out to be the Birmingham keeper next season, he will do a good job.'
Hart wanted to remain at Birmingham but accepts the final say was with Manchester City.
He said: 'I just waited for my orders, and my orders were that I went back. I am contracted to Manchester City so that's where I will be.
'I will admit, it's sad. But it was out of my hands. If I could have stayed at Birmingham, I would, but it wasn't down to me.
'I didn't really want to leave but I was told that I have to. It's just the way football is.'
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