These small headed racquets seem to be from a bygone age. No doubt he sticks with it, simply because that's what he's used to and grown up playing. If he moved to a a slightly larger headed, less demanding frame, he really should not be a risk of being overpowered or being forced onto the back foot as much against the likes of Nadal and Djokovic. Even a mishit might just trickle over the net rather than being an inch or two below the tape. 88/90sq" just acts as a disadvantage to him. Federer is a wonderful talent, and if he was at the peak of his powers, then fine, but he is in (or approaching) the autumn of his career, he's never been hugely successful on slower courts, and is showing some fallibility. Why make life more difficult with a demanding small headed racquet? He's the only person at the upper levels that plays with such a stick. People will talk about all the slams he won but nobody doubts his greatness. But the peak of those slams were a few years ago when he was younger, at the peak of his powers, and the competition wasn't quite as fierce. Annacone's got him to try and shorten the points and play more of an attacking game, and whilst there's nothing wrong with that, he's going to have to be almost pitch perfect in every stroke that he hits at the top 2 or 3 players to carry that off. Just being a fraction off or having a day where's he's not quite 100% is going to produce the sort of higher error count that visible during the Djokovic match. I remember Annacone floated the idea of a racquet change with Sampras and the only reason Sampras didn't change was because it was what he was used to and was wary about transitioning his game when at a stage where his career was already 'time limited'.