Taylor Fritz moved closer to the semis of the season-ending ATP Finals after the American beat Alex de Minaur 5-7 6-4 6-3 in their last group game on Thursday, but he will have to wait and see if Jannik Sinner can take a set off Daniil Medvedev.
The match also marked the first time a deciding set was played at this year's tournament as Fritz bounced back from a set down with a dominant display in the second before running away with the third set.
U.S. Open runner-up Fritz can qualify for the final four if Sinner takes a set in his match against Medvedev. But the American will be eliminated if Medvedev beats Sinner in straight sets.
Seventh seed De Minaur, meanwhile, goes home without winning a single match in the Ilie Nastase group on his tournament debut.
"He was all over me (in the first set). What I did a great job of was in the second set, towards the end of the second set, I really started to find my serve," Fritz said.
"I started serving much better and then that allowed me to just stay with it and create more pressure on his service games... It just gave me a little bit of comfort to just stay in the match and not be under so much pressure all the time."
The two played some entertaining tennis in the opening set, including a 30-shot rally which De Minaur won with a passing shot while Fritz walked back to the baseline with a wry smile.
De Minaur converted the all-important break at 5-5 and served for the set, sealing it with an ace, which also confirmed world number one Sinner as the first semi-finalist.
De Minaur, however, needed to win the second set comfortably to stand a chance of advancing to the semi-finals and the Australian saw his slim hopes of going through evaporate when Fritz levelled the score at one set apiece.
That was all the motivation a fired-up Fritz needed as he raced into a 4-1 lead to gain control of the decider while De Minaur crumbled. At 5-3, Fritz had three match points and took the contest with an ace.
"I think all of us are pretty beat up, but if I'm in the semis of the World Tour finals, I've got energy to give it for the semis," Fritz added.
