The Spurs loanee was left out of the 1-1 draw at Millwall on Saturday.
"Benoit been up and down," Redknapp told the Fulham Chronicle. "I don't think he's found the level he had at Tottenham. I think he's found it difficult the change between the Championship and the Premier.
"I was watching a bit of the 2010 Premier, and there was Benoit crossing balls - to Niko (Kranjcar) as it happened.
"He was one of the best three left-backs in the Premier League, but he hasn't risen quite as high. In bits and pieces, hopefully he'll be a big player for us in the play-offs."