Stanislas Wawrinka, who won two of his three round-robin matches at the ATP World Tour Finals, says stronger self-confidence is a key to his success this season.

“It's like a puzzle,” Wawrinka said. “You have to put all the piece together. When you win, you get more confident, so you feel better on the court. When I feel good physically, I can play better tennis, so technically I'm much better. It's a lot of small things that make huge difference.

“But for sure I think this year the most important was my self‑confidence on the court. Now when I come on the court, even against Berdych, against Rafa, against Ferrer today, I know that I can beat them. That's already a big step ahead.”