Jannik Sinner battles past Taylor Fritz to claim second win in Turin at ATP Finals
In a repeat of September's US Open final, home favourite Sinner delighted a raucous crowd with a 6-4, 6-4 victory in the best match of the tournament so far.
American world number five Fritz went toe-to-toe with Sinner throughout a contest ultimately decided by slender margins with one break of serve in each set.
Sinner made the decisive break in the opening set when Fritz served at 4-5, bringing up a set point with a disguised drop shot and then converting at the first opportunity.
Fritz refused to go away in the second set but cracked under pressure as he served to stay in the match.
"It was a very tough match, we both knew exactly what to expect," Sinner said after his 67th victory of the season.
"He was very aggressive. I managed to serve very well in the crucial moments. I'm happy how I handled the tough situations like at 3-3 in the second set when the momentum could have changed if he had broken me."
Earlier in the Ilie Nastase Group, Russian Daniil Medvedev earned his first win of the week as he beat Australia's Alex de Minaur to keep himself in contention for a semi-final spot.