Redknapp is convinced they can still avoid relegation.
He told Sky Sports: "We've got a challenge on and if we can pull this one off between us, the players, myself, the owners the fans, it will be a great achievement from everybody's perspective, and we're all looking forward to giving it a go.
"This probably would be (my biggest challenge ever). Going back to Portsmouth was a difficult one when I went back there having left and then having gone back, if I hadn't kept them up that year, I wouldn't be stood here now.
"It's a tough one but I think we can do it. If we're clever in the window, we can get a couple in and they could make a little bit of difference to us."