Alexander Zverev boosted his chances of reaching the semi-finals of the Nitto ATP Finals with a three-set win over Diego Schwartzman.
Zverev, the 2018 champion, was dejected after losing to Daniil Medvedev in his opening match, and there were plenty of holes to pick in this performance, too, but the German emerged a 6-3 4-6 6-3 winner.
Argentinian debutant Schwartzman was staring at a second convincing loss after Monday's defeat by Novak Djokovic when he trailed 3-1 in the second set and faced points for a double break.
But he fought back to win five out of the next six games and take the match to a decider. It was Zverev who stepped up when it mattered, though, winning five of the last six games to end the match.
The German will need to beat Djokovic tomorrow to have a chance of reaching the last four, and will surely need to play at a consistently-higher level.
He said in his on-court interview: "It was much better than on Monday. Diego's a very difficult player.
"I'm happy to get the win, I'm happy to give myself a chance. Friday is going to be the most difficult match you can have here against Novak. I'm looking forward to it."
Schwartzman has had his best results on clay, including a run to the semi-finals of the French Open last month, so he was always likely to have his work cut out to win matches this week.
He said: "I have to learn about this tournament. Everything is new. Today I think I did better but in this surface, they like the surface. I think most of the guys who are here, the best surface they play is indoor courts, and I think at the end today it made the difference. But I'm happy because I improved."
And there was a real shock in last night's second match as Djokovic lost in staight sets to Daniil Medvedev.
Medvedev won 6-3, 6-3 to seal his place in the last four and now Djokovic must beat Zverev for a semi spot.