Jannik Sinner remains unbeaten at the ATP Finals in Turin. (Getty Images: Valerio Pennicino)
In short:
Jannik Sinner will play Alex de Minaur in the last four at the ATP Finals.
Sinner defeated Ben Shelton in his final group match, 6-3, 7-6 (7/3).
De Minaur is coming off a straight-sets win over Taylor Fritz.
Reigning champion Jannik Sinner says he will need to produce his best tennis to get past Alex de Minaur in the semis at the season-ending ATP Finals.
Italy's Sinner extended his winning streak on indoor hardcourt to 29 matches with a 6-3, 7-6 (7/3) victory over American Ben Shelton in their round-robin match at Turin's Inalpi Arena.
Earlier this week, de Minaur had been the picture of dejection after feeling he had thrown away a victory against Lorenzo Musetti when in a winning position.
Musetti triumphed 7-5, 3-6, 7-5.
Four-time major winner Sinner has won all 12 matches he has played against de Minaur, but is refusing to take the world number seven lightly.
"I'm very happy for Alex, because when you have the type of losses he had against Lorenzo, it's very tough," Sinner said after his defeat of Shelton.
"But props to him to come back with such an incredible performance, one of the best matches I've seen him play, against Taylor.
"So I have to be very careful because he doesn't have a lot to lose. I have a lot to lose, so it's going to be very difficult.
"But I'm very happy to be in the semis and, hopefully, I can show some good tennis and we can hope for a couple of great semis."
The other semi will be between Carlos Alcaraz and Félix Auger-Aliassime.
Canadian Auger-Aliassime defeated Alexander Zverev 6-4, 7-6 (7/4) to earn a spot in the last four.
Before Sinner's match with Shelton, Alcaraz was presented on court with the ATP year-end world number one trophy.
"It's a pleasure being the number one of the world, it's something that I'm working really hard for every day, it is a goal to be honest," Alcaraz said.
"For me, it's a great achievement. It means the world to me and I'm just really proud and happy."