The two Italians met in what initially looked like a one-sided battle.
Sinner also started the match at a furious pace and went up 2–0 early in the set.
Then Darderi, ranked 22nd, fought back and improved his game in the third set. However, it was not enough. Sinner took the set 7–6 and is on to the quarterfinals.
Sinner will face American Ben Shelton, ranked eighth in the world.
The quarterfinals will be played on Tuesday, when high temperatures are expected. Temperatures could reach 44 degrees Celsius, and according to the organizer's rules, referees can stop play or order additional fluid breaks in extreme weather.
