Matteo Berrettini of Italy advanced to his first Grand Slam quarter-final by beating Russia's Andrey Rublev 6-1 6-4 7-6(6) at the US Open.
Berrettini, seeded 24th, made use of his big forehand throughout the match, hitting 17 forehand winners on the Louis Armstrong Stadium court.
"My weapons were really good today," said Berrettini who hit a total of 37 winners. "I was mixing up my tennis."
The 43rd-ranked Rublev, with wins against Swiss pair Roger Federer and Stan Wawrinka in Cincinnati last month, went into Monday's match as the slight favorite.
But the Russian struggled with his first serve through most of the match, managing to get only 56% of first serves in and losing 67% of those he landed.
Berrettini faces the winner of Monday's later match between France's 13th seed Gael Monfils and Pablo Andujar of Spain.
Daniil Medvedev revelled in his role as the villain of the US Open after beating Dominik Koepfer to reach the quarter-finals.
The Russian fifth seed, who caused a stir by sticking his middle finger up at the crowd in a 'visible obscenity' two nights earlier, was jeered as he strode onto court in Louis Armstrong Stadium.
The majority of the spectators were firmly behind German qualifier Koepfer when he went a set and a break up.
But Medvedev eventually won 3-6 6-3 6-2 7-6 (2), before goading the crowd again with his celebration and then saying in his courtside interview: "Guys, continue to give me this energy. You are the best."
ESPN commentator Pam Shriver, referring to the mutual respect shown between Naomi Osaka and Coco Gauff 24 hours earlier, said: "The women are being so well behaved, and the boys are just misbehaving. Boys will be boys."
Earlier, Roger Federer laid down a marker by dismantling David Goffin to reach the quarter-finals.
The third seed dropped just four games, winning the last nine on the trot, for a brutal 6-2 6-2 6-0 victory in just an hour and 21 minutes.
