Andy Murray is in the middle of one of the hottest streaks of his career.
He's just replaced the formidable Serbian Novak Djokovic as world number one, having won Wimbledon and the Olympic gold medal in Rio, and has won 20 matches in a row ahead of his clash with Kei Nishikori.
Murray is also the favourite to win the ATP World Tour Finals, despite a poor record at the tournament down the years.
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In seven tournament appearances, the Scot has reached the semi-finals on three occasions, but has never advanced to the final.
For a player of his quality and record in other major tournaments, the two-time Olympic Champion will be disappointed with a return like that.
This year seems different, though, as he tops the world and main opposition Djokovic has been faltering of late.
After a successful start against Marin Cilic, Murray has been taking on Nishikori, a player he's beaten six out of the seven times they've met.
Defending set point, Murray pulled out all the stops to save the point, producing some phenomenal tennis to deny the Japanese.
After a forceful backhand volley from Nishikori, Murray sprinted to his left and stretched to backhand the ball beyond the reach of the world number five, saving the point.
In spite of this, Nishikori would still go on to take a set lead over the three-time Grand Slam winner, with the match still progressing as of writing this article.