Roger Federer, asked by BBC Radio Five Live what goes through his mind while playing a point:
"Of course, you know the strengths and weaknesses of your own game, strengths and weaknesses of your opponent's game so you can prepare a point by saying 'OK, I'm going to serve to his backhand and normally the chances are and then you put it in per cent and say 'it's probably going to come back to my backhand' and you start to rally like this and then the chances are... But
you can't do it before every point. If it doesn't happen the way you thought, you get surprised.
"You have to expect the unexpected in tennis because every opponent is different, there's the lucky shot – the frame, the bounce, the net cord – the elements of the wind, the sun.
"So sometimes it's better to let it go and play shot for shot and just read the situation... compress it all down to the next shot of the next point. When it goes well, you don't ask yourself too many questions. When it goes badly, that's when you start to think too much and that's when it gets complicated."