Australian whiz-kid Alex de Minaur will go into the last four of the Next Gen ATP Finals undefeated after beating American Taylor Fritz.
Second seed de Minaur was at his gritty best to save five set points in a tiebreak and claim the opening set before running away with a 4-3 (10-8), 4-1, 4-2 victory in his final group stage match in Paris.
"I just had to dig deep," the 19-year-old said on Thursday after entering the semi-finals having dropped just one set.
"I was down and out there and I managed to scrap my way [back] with a couple good returns and a couple long rallies."
"I managed to get that one cheap point and was able to serve it out so that first set was crucial."
The Sydneysider had already booked his spot in the semi-finals on Wednesday with a four-set win over 2017 runner-up Andrey Rublev after earlier thrashing Italian wildcard entrant Liam Caruana.
De Minaur, the 21-and-under tournament's youngest entrant, now faces sixth-seeded Spaniard Jaume Munar for a place in the final.
His clean sweep of the round-robin stage has taken his season earnings past $US1 million ($A1.4 million).
But the young gun could almost double his 2018 prize money in the next two days, with a $US407,000 payday on the cards if he finishes the tournament unbeaten.
First seed Stefanos Tsitsipas remained on course to potentially challenge de Minaur with a 4-1, 4-3 (7-2), 4-1 win over Poland's Hubert Hurkacz.
The Greek world No.15 will meet Rublev in the semi-finals after the Russian finished second in his group with a three-set win over last-placed Caruana.