German giant Zverev put his height to good use as he smashed 18 aces past the American in a 6-4, 7-5, 6-2 victory in just one hour and 40 minutes.

Last year's US Open runner-up brilliantly employed a rarely seen serve-and-volley style of play on the Arthur Ashe Stadium, winning 90 per cent of points on his first serve as well as 92 per cent of net points.

He was also assisted by his opponent's 28 unforced errors which helped to relieve pressure in key moments, and is now scheduled to play Albert Ramos Viñolas of Spain in the second round.

Djokovic is looking to become the first man since 1969 to win all four of tennis’ Grand Slams in a single year, but was tested by the 18-year-old Dane Rune, requiring four sets to progress 6-1, 6-7, 6-2, 6-1.

The Serbian is now scheduled to face the Netherlands’ Tallon Griekspoor in the second round.

Wimbledon finalist Matteo Berrettini progressed in straight sets against Frenchman Jérémy Chardy.

The victory was not as one-sided as it first appears as the sixth seeded Italian was pushed to a tiebreak in the first two sets but held his composure to win 7-6, 7-6, 6-3.

Canada's Denis Shapovalov breezed past Federico Delbonis of Argentina 6-2, 6-2, 6-3 to join his compatriot Félix Auger-Aliassime in the next round.

After a strong start from the Argentine, the momentum was completely in Shapovalov's favour from the fifth game until the end of the match.

Another seeded player, Hubert Hurkacz of Poland also won in straight sets.

The 10th seed beat Belarusian Egor Gerasimov 6-3, 6-4, 6-3 with an impressive 14 aces and zero double faults.

Italy’s Jannik Sinner, seeded 13th, progressed with a 6-4, 6-2, 4-6, 6-2 against New Zealand’s wildcard entry Max Purcell.

Spain’s Pablo Carreño Busta, the ninth seed and Olympic bronze medallist at Tokyo 2020, became the highest ranked casualty of the tournament so far as he let a two-set lead slip against American qualifier Maxime Cressy.

Cressy held his nerve to clinch the deciding tiebreak by nine points to seven, and progress 7-5, 6-4, 1-6, 4-6, 6-7.

World number 28 Karen Khachanov, a silver medallist at Tokyo, also suffered an upset to South African Lloyd Harris in a five-set thriller.

Harris beat the Russian 6-4, 1-6, 4-6, 6-3, 6-2, in three hours and seven minutes after showing incredible tenacity to stage a comeback.

Belgium's David Goffin was another to falter at the hands of an unseeded player as American Mackenzie McDonald humbled the 27th seed 6-2, 7-5, 6-3.

Another American in Taylor Fritz defeated 14th seed Alex de Minaur of Australia to ensure the host nation has 13 players in the second round - the most it has had since 1994.