Cahill recounts Federer's training routine: "I was amazed at how hard he worked on the court"

Darren Cahill, co-coach of current world No. 1 Jannik Sinner, was a guest on entrepreneur Brad Sugars' podcast last year, where he discussed Roger Federer's work ethic.

Invited to follow the Swiss's training sessions, Cahill has a vivid memory: "It was many years ago in Dubai, I had spent a week with him. I was amazed at how hard he worked on the training court.

Four-, five-hour blocks. I never knew that about Roger. Because if you see him warming up before a match, you get the impression he's going to play with the country club boys.

He just hits the ball, barely moves his feet. And he said to me, 'Darren, all the work is done in preparation. I just have to feel the ball and feel good about my game.

So it's all done out of sight. And that's where all the work is done. The court is just a backdrop.

What counts is when you train in a stadium where there are zero people watching you. That's when you put everything into it."