Redknapp is eager to bring a new left back to Fratton Park with Matt Taylor missing the start of the season with a heel injury, and had targeted Chelsea's Le Saux.
The experienced defender has little chance of first-team action at Stamford Bridge with the impending arrival of Wayne Bridge, who has passed his Stamford Bridge medical, and is ready to move on.
Redknapp was looking to bring the 34-year-old in on a £500,000 deal, but says he is likely to lose out to near neighbours Southampton.
Saints boss Gordon Strachan is looking to take Le Saux as a replacement for Bridge, and Redknapp admits he will probably move to St Mary's
"We need to get a left back in because Matty Taylor is going to be out," said Redknapp.
"Graeme Le Saux is one player we've looked at, but I can't see it happening because it looks like he's off to Southampton."
