Rafael Nadal could get a helping hand from Roger Federer in his bid to end 2019 as the year-end No 1.
Nadal was 5-1 and a match point down in the final set of his match with Daniil Medvedev.
But the world No 1 staged a miraculous comeback to get both of the breaks back and force a tiebreak.
And the Spaniard was the better player in the breaker as the pressure got to Medvedev and he completed the turnaround when the Russian’s backhand went long.
It means Nadal’s hopes of winning a first ATP Finals title and becoming the year-end No 1 remain alive.
And his great rival Federer can help him seal the No 1 ranking if he beats Novak Djokovic on Thursday night.
Djokovic must reach the final and win it to give himself a chance of ending the year ranked No 1 for the sixth time.
If Djokovic does beat Federer tomorrow, Nadal can still get the job done himself by simply reaching the final.
Speaking after the match, Nadal played down suggestions that the comeback over Medvedev was one of his best-ever performances.
“No, no, is not one of the best performance of my career, no? Not at all. I really hope that I can play better,” he said.
“I have been better than the other day, of course. I have been playing a better level of tennis than the first day in general terms.
“Then win this match is a combination of a lot of things: lucky, some mistakes of Daniil, some good moments of myself at the end.
“But in general terms, knowing that I was not able to practice the way that I would like before the tournament, be able to increase the level since two days ago to today like this is a very positive thing and I’m very happy with this. Win or lose is another story.
“Daniil is super tough mentally. He showed everybody during all this year what he achieved. If you are not able to be very solid mentally, is impossible, honestly.
“So today is one of these days that, as I said on the court, one time of one thousand you lose this match, and it happened today.
“Very happy for that. Very sorry for him, honestly, because to lose a match like this is tough, and it’s painful.”