David Moyes has been without Phil Jagielka and Mikel Arteta during the campaign and head into the weekend 16th in the table, while Spurs recently suffered defeats when Jermain Defoe was suspended and Aaron Lennon was in the treatment room with Luka Modric.
Defoe and Lennon are back now and will spearhead Redknapp's attack at Goodison Park on Sunday as Spurs look to cement their place in the top four, and Redknapp said: "They have had injuries this year, and I think that's been the key. They've lost some key players. Arteta, for me, was their main player, he made them play and is a fantastic footballer who they miss badly."
He added: "But they have got a strong squad, when they're all fit they've got a very powerful squad."
Spurs hope to break into in the top four this season, with Liverpool and rivals Arsenal looking vulnerable. Arsene Wenger has also lost a key player in Robin van Persie.
"Two or three weeks ago everyone was saying how fantastic Arsenal were," Redknapp said. "But Van Persie got injured. That's how important your key players are to you. Nicklas Bendtner is injured and suddenly they've got no focal point."
Another key player for Redknapp is Jonathan Woodgate but Redknapp does not know when his centre-back will return after suffering a groin problem.
Woodgate, 29, suffered with the complaint last season and travelled to Germany for an operation in August but the problem has not gone away despite a recent injection.
The former Real Madrid defender has only completed two games this season, the recent Barclays Premier League wins over Sunderland and Wigan, and is back on the sidelines again.
"He's had the injection but it doesn't seem to have done the trick really," Redknapp said. "I don't know if he can have another operation, he's had so many. I don't know what the next step is really. At the moment, Woodgate is not training
