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.

Federer had looked susceptible in his opening two matches, dropping a set in both, but is since cruising through the gears.

Goffin, who broke Federer's serve early in the first set, won just seven points in the third, the Swiss finishing him off with a stunning backhand pass down the line.

Federer, looking for a 21st grand slam title, said: "Look, sometimes these scores just happen. You catch a good day, the opponent doesn't, then things happen very quickly.

"Maybe he struggled a bit early on. But I found my groove after a while and was able to roll really, and never looked back.

"David wasn't nearly as good as I expected him to be. He was struggling a little bit. I was able to take advantage of it, and I think that's the key.

"In a fourth round like this, if you can keep it nice, short, simple, you have to take them. I'm very happy."

Federer will face Grigor Dimitrov, the former world number three, in the last eight.

Bulgarian Dimitrov beat Alex De Minaur of Australia in straight sets, 7-5 6-3 6-4.