Saha joined Tottenham just before Tuesday night's 11pm deadline in one of the surprise moves of the January window.
The Frenchman replaces Roman Pavlyuchenko, who is heading for Lokomotiv Moscow for £8million while Steven Pienaar returned to Goodison Park for the rest of the season following Saha's exit.
Many have questioned Redknapp's judgement in bringing in an injury-prone striker past his prime, but he has a history of turning players who are supposedly over the hill in to good performers.
Redknapp reinvigorated the career of Paolo di Canio at West Ham, somehow managed to get Kanu scoring goals while he was at the twilight of his career at Portsmouth, and has also got the best out of 34-year-old William Gallas since he arrived from Arsenal two summers ago.
Redknapp is confident that he has not taken a gamble by signing Saha. He said: "He's got good movement, can score goals but probably needs a change. He's out of contract at the end of the year so (Everton boss) David Moyes has let him go.
"I can remember speaking to Rio Ferdinand and he said he was the best forward he'd played against."
Tottenham shipped out Sebastien Bassong on loan to Wolves and were awaiting confirmation on Wednesday night that their bid to sign Blackburn's veteran defender Ryan Nelsen to replace him had gone through.
Nelsen, 34, was out of contract at the end of the season and has only played once for Rovers this term, making him an even more surprising choice than Saha.
Redknapp insists the New Zealander will have a big impact at Tottenham if the deal goes through, however.
"I think he's a great competitor and a good sort to have at your club," Redknapp said after Tuesday night's 3-1 win over Wigan.
"I have always liked him."
The arrival of both players is welcome given that Redknapp saw his injury list increase.
Rafael van der Vaart (calf), Kyle Walker (groin) and Emmanuel Adebayor (hamstring) all hobbled off through injury and are doubts for Monday's game at Liverpool.
Spurs are already without long-term absentees Gallas (calf) and Tom Huddlestone (ankle), while Michael Dawson has only just returned from an Achilles layoff.
The only other bits of business concluded at Tottenham saw Vedran Corluka join Bayer Leverkusen until the end of the season and youngster Adam Smith sign for Leeds on loan for the rest of the current campaign.