Redknapp came back to Fratton Park in December 2005 after a year managing local rivals Southampton and had to endure cries of "Judas" from the Pompey supporters, but he steered them clear of relegation.
He said: "It wasn't easy and I have no doubt if we had gone down I wouldn't be here now talking about an FA Cup final win.
"When I looked at the quarter-final draw and saw we'd got Manchester United away I thought that was that again but we got a 1-0 win up there, kept a clean sheet and got none of the credit we should have done.
"But I think the players have deserved this and so have I, even though I feel for Dave Jones who I've got a lot of time for.
"Kanu has been fantastic for us. That's a semi-final and a final he has won with his goals and yet when I signed him at the start of last season on a free transfer from West Brom people said I was mad.
"I thought when he missed the first chance today it could be costly but he keeps on going, keeps on trying to do the right things and he's a big plus for us."