Gestede has dropped out of favour since Garde took charge at Villa Park, but he showed his class by scoring against Leicester City on Saturday to help his side pick up a 1-1 draw.
And Redknapp feels that Garde should be picking the former Blackburn Rovers man more often - as he feels he is a striker who looks like scoring when he is on the pitch.
"Whether Remi Garde thinks he's an impact sub I don't know, but they look a better side to me when he's in the team," Redknapp said. "He looks like he's going to score.
"In the second half when they played two up front they had a focal point and looked like something might happen. It might not be pretty and it might not be how [Garde] wanted to play when he managed teams in France, but it's a case of needs must and that might just be their way of staying up. I don't think they will, but at least you can see signs that way.”
Gestede was introduced as a late substitute for Villa against Leicester, and his bludgeoning approach paid dividends.
With both Libor Kozak and Gestede up front, the Villans were able to play far more directly, and they posed a threat against the Foxes.
They got their reward for showing attacking ambition when Gestede grabbed an equaliser, but the draw does little for their survival chances.
Villa are under pressure to start collecting victories at a rapid rate, as they are currently nine points away from safety with time running out this season.