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.

"All of us are pretty beat up but if I'm in the semi-finals of the world tour finals then I've got energy to give," said Fritz.

Seventh seed De Minaur, although labouring through his opening service games, was the first to break when he ended a superb rally with a clever cross-court winner for a 4-3 lead.

Fritz was quick to respond, levelling in the next game before De Minaur broke again and served out the opening set as his opponent became increasingly frustrated, complaining to the umpire about flash photography in the arena.

The US Open runner-up had to fend off two break points in the second set, while De Minaur, in comparison, looked comfortable on serve with three love holds.

That was until Fritz increased his intensity and seized his opportunity at 5-4 to end De Minaur's season.

With his tournament essentially over, De Minaur continued to falter as Fritz surged and he wrapped up the victory with an ace after two hours and eight minutes.

"He was all over me. What I did a great job of was towards the end of the second set I started to find my serve, I started serving much better," Fritz said.

"It just gave me a little bit of comfort to stay in the match and not be under so much pressure. It was still incredibly tough."