Taylor Fritz boosted his hopes of reaching the last four of the ATP Finals with a comeback victory against Australia's Alex de Minaur.
De Minaur needed to defeat the American fifth seed in straight sets for any chance of progressing to the semi-finals in Turin, Italy.
However, his hopes were crushed when Fritz stole the second set against the run of play.
Fritz, who went on to win 5-7 6-4 6-3, will progress to the last four of the season-ending tournament if Jannik Sinner beats Daniil Medvedev later on Thursday.
If 2020 champion Medvedev wins in straight sets, the Russian will advance as group winner ahead of Italy's world number one Sinner, while Fritz will miss out.