Redknapp declared: "We had no real problems for the first half-hour but then Frank does what he does better than anybody else. He ran off his marker and gambled that he would get on the knock-down and that's exactly what he did.
"That's what he does week in and week out and we expected him to do that but it was the one time we didn't pick him off. But we had some good chances. We have made unbelievable progress in 18 months."
Pompey's England goalkeeper David James looked at fault for Lampard's goal after not getting a strong enough hand on the ball to prevent it going in.
But although Redknapp was aware that the blame could be heaped on James, he insisted he would have to wait until he had seen it on TV to have a view about it.
But even so, Redknapp full of praise for the 37-year-old who is in the running to reclaim the England number one jersey from Paul Robinson for the Euro 2008 qualifiers against Israel and Russia next month.
Redknapp said: "I haven't seen it since. It might have taken a deflection but I am not sure. David is normally quite harsh on himself but he has not said anything.
"David has been fantastic for us. He's form has been unbelievable. Playing for England means a lot to him but then it does for Paul Robinson, they all want to play.
"David has been a great signing. When I signed him there was a of doubters but he's been top class."