Federer switched to a 97 square-inch frame in 2014 – a move he credits for his upturn in form.
The 19-time Grand Slam champion is able to unleash more powerfully on his one-handed backhand than before while his serve is also far more dangerous.
Sky Sports pundit Rusedski said: “It was very brave to change the racket. He talked to Pete Sampras about it because they both had the same coach Paul Annacone.
“Pete always said ‘I wish I’d change to a bigger frame’ and Roger was willing to do that.
“He hurt his back with Paul Annacone when he went through that change and he put it on pause a little while and then did it.
“That’s the genius of Roger. He’s always looking to get better.
”He loves what he does. I remember at the end of my career he was walking out of the locker room laughing and joking.”
Speaking about the change earlier this year, Federer said: “I think the backhand has gotten better because I have been able to put in so many hours onto the racket.
“And since this year, I feel super comfortable with the racket, and I think I have gained confidence stepping into it.
“I think it was the work that I had in [the offseason]. You never play 10 backhand-to-backhand shots, but in practice you practice those a ton and eventually they are ingrained in the system.
“You need good footwork, because if the footwork is not good, you won’t be on top of the ball.”