Despite playing six sets in the tournament, Sinner remains undefeated, even though his matches have been frequently interrupted. In his match against Mannarino, Sinner had to wait nearly three hours to start the second set due to a rain delay. Earlier, in the third round, his match against Gabriel Diallo was also interrupted by a false fire alarm.

Sinner hits a forehand during his match against Mannarino in the fourth round of the Cincinnati Open in Ohio, USA on 13/8. Photo: Reuters

Sinner hits a forehand during his match against Mannarino in the fourth round of the Cincinnati Open in Ohio, USA on 13/8. Photo: Reuters

These incidents didn't affect Sinner's performance. A prime example was his excellent backhand winner when leading 4-2 in the first set. The second set proved more challenging for the Italian player as his first-serve percentage dropped to 52%. However, Sinner's top-ranking composure shone through in the tie-break, which he won 7-4.

After the one hour and 48-minute match, Sinner extended his winning streak on hard courts to 24, surpassing Novak Djokovic's 23-match streak in 2015. This places him eighth on the list of longest unbeaten streaks on hard courts in the 21st century. Sinner's last defeat on a hard court was against Alcaraz in the final in Beijing last year.

This year, Sinner has lost only three out of 32 matches. The 23-year-old will reach the 30-win mark if he defeats Felix Auger-Aliassime in the Cincinnati Open quarterfinals.

Alcaraz also secured a spot in the quarterfinals. Against Nardi, Alcaraz won 13 of the first 14 points and finished the first set in just 27 minutes. The second set saw a different dynamic as the world number two trailed 2-4. Alcaraz calmly leveled the score and created a turning point in the 9th game. He won the game after eight deuces, while Nardi double-faulted on the final two points.

Alcaraz's next opponent is Andrey Rublev, who defeated Francisco Cerundolo 6-2, 6-3. Alcaraz leads Rublev 3-1 in head-to-head matches, including a victory in the fourth round of Wimbledon last month.

Vy Anh