World No 1 Jannik Sinner made it two wins in a row at the ATP Finals with a 6-4 6-4 success against Taylor Fritz in a rematch of the US Open final.
Fritz put the world No 1 through his paces in the early stages of a fabulous contest at the Inalpi Arena in Turin.
The 23-year-old, however, raised his game when required to register a big win to improve to 23-1 in his last five tournaments.
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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 got to know each other very well in a Grand Slam final," said Sinner. "We knew exactly what to expect today, he was very aggressive and I was prepared.
"I just tried to serve very well in the important moments, which I did. That was a very crucial game in the second set, I was down 0-30. If he breaks me there, the momentum could change."
Sinner will seek to extend his perfect 2-0 record in the Ilie Nastase Group when he takes on fourth seed Daniil Medvedev on Thursday.
Fritz, who is 1-1, aims to secure a crucial win against Alex de Minaur in his bid to advance to the semi-finals.
Henman: It's another impressive win for Sinner
"Taylor Fritz's tennis was very, very impressive. There were 20 games and in 18 of them it was so, so tight," Tim Henman told Sky Sports Tennis.
"If anything there were times when Fritz had the upper hand but he was never able to create the full chance from the half-chance and when Sinner got his opportunity at the end of each set he was able to take it.
"The scoreboard pressure of serving first in each set gave Sinner that advantage. It's another impressive win for Sinner. He is showing us why he's the best in the world right now."
Tale of the Tape
Sinner vs USA
Ruthless Medvedev defeats De Minaur
Medvedev claimed a dominant 6-2 6-4 victory over De Minaur on Tuesday to move back into contention.
Medvedev came into the fixture after a dramatic loss against Taylor Fritz on Sunday where he lost his temper, smashed his racket, and earned a penalty point for smashing a courtside microphone, but the fourth seed looked considerably calm during his straight-sets win over De Minaur.
Medvedev only made 10 unforced errors and conceded just nine points on his serve as he wrapped up his victory in an hour and 18 minutes to extend his record to 7-3 over De Minaur.
"After the last match, I was too tired to fight mentally the way I do and so during the match when it doesn't work your way, you want to win and when you start losing you get frustrated," said Medvedev after his win.
"So I went into this match thinking, if I lose I go home on Thursday for sure and if I win then I have the chance to have a good feeling.
"I tried to hit some shots and it worked well and I'm okay with it.
"I went into this match trying to block the noise even from myself so no tantrums and I really didn't care what was happening on the court."
Robson: Medvedev had more firepower
"Medvedev was a totally different player, no reaction, no fist bumps, just a solid mentality start to finish," said Sky Sports' Laura Robson.
"He was watching his own highlights and his stats and was in totally different mood and had more firepower to his game.
"His backhand was catching De Minaur off guard and his serve was better.
"Medvedev was talking about matches becoming a bit monotonous whereby you play guys who all move well, who all hit the ball well and play the same point over and over.
"He said it feels mentally draining because of how each point is played.
"Maybe that's because of the serve because it's gone up and down this year and the way the ball toss is moving a bit forward."
Tale of the Tape
How the Ilie Nastase Group looks...
Will Alcaraz be fit for Wednesday's clash at Nitto ATP Finals on Sky Sports Tennis?
- World No 3 Carlos Alcaraz hopes to be fit for must-win clash against Andrey Rublev (from 1pm GMT)
- Two-time former season-ending champion Alexander Zverev takes on Casper Ruud (not before 7.30pm)
Alcaraz's participation in Turin has been cast into doubt after he pulled out of practice with illness.
His coach Juan Carlos Ferrera told Spanish media the 21-year-old cut short his session after just five minutes as a chest complaint was making breathing difficult.
Britain's Henry Patten and partner Harri Helioevaara are on the brink of the doubles semi-finals after a second straight win, beating Australians Max Purcell and Jordan Thompson 7-6 7-5 in a repeat of their Wimbledon final.
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