Alexander Zverev, of Germany, serves to Alejandro Davidovich Fokina, of Spain, during the fourth round of the US Open tennis championships, Sept 6, 2020, in New York. (SETH WENIG / AP)

NEW YORK - Alexander Zverev slammed down 18 aces en route to demolishing Alejandro Davidovich Fokina 6-2 6-2 6-1 in the fourth round of the US Open on Sunday.

Widely presumed favourite to win the US Open, Novak Djokovic, was disqualified from the tournament after striking a line judge with a ball 

After an early break for the 2-1 lead, the 23-year-old German never let his Spanish opponent get a foothold in the match. He produced 39 winners and dropped just one service game during a ruthless performance.

Davidovich Fokina grabbed a 2-0 lead in the second set but the advantage was shortlived as Zverev broke back before racing away with the set. He sealed it with an ace.

The Spaniard barely had a chance to make an impact on the world number seven’s serve, the fastest clocking at 139 mph, just shy of his personal record of 142 mph.

Davidovich Fokina, who took a medical time out to treat a foot problem, tried to rattle Zverev by attempting some drop shots but the fleet-footed fifth seed moved nimbly around the court.

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The win was overshadowed by a shocking incident one court over, as top seed and widely presumed favourite Novak Djokovic was disqualified from the tournament after striking a line judge with a ball following a point during the first set of his match against Spain’s Pablo Carreno Busta.

A stunned Zverev went ahead with a previously scheduled press conference minutes after the incident.

“It’s very unfortunate that, you know, he hit the line judge, and especially where it hit her,” he said. “I don’t know what to say. I’m a little bit in shock right now, to be honest.”

Zverev, who reached the Australian Open semi-finals earlier this year, was among the favourites to contest Djokovic at this year’s competition.