Redknapp told The News: "It's hard to believe what is happening at Manchester City really. What will happen in this country in years to come is you will have 20 billionaires owning football clubs and they will all want to win.
"But they can't all win. They can't understand why they are seventh or eighth, but for Manchester City it's a massive improvement - the best they've done in years. The more foreign owners that come in, the worse it will get - they will all want to be in the top four.
"I think the people of Portsmouth are very fortunate to have him."
Since arriving at Fratton Park in January 2006, firstly as joint owner, Gaydamak has faced a steep learning curve.
Redknapp said: "He's learning the game. He's not got a great knowledge of football, but he's learning and he's enjoying it. When he first came in, he thought 'What's going on - why are we not winning?'
"I said to him 'we are not winning because we're not good enough. We will get relegated.' He understood that, then we bought the three lads from Tottenham and Benjani, they improved us and we stayed up.
"But Sacha has learnt as he's gone along. He's supportive, doesn't interfere and he's improved everything here."