World No.1 Novak Djokovic has eased past Bosnia and Herzegovina's Damir Dzumhur 6-1 6-4 6-1 to reach the second round of the US Open at Flushing Meadows in New York.
Played in front of an empty Arthur Ashe Stadium due to the COVID-19 pandemic, the Serb cruised for long periods to extend his 2020 winning streak to 24 matches.
Greek fourth seed Stefanos Tsitsipas has kicked off his quest for a maiden Grand Slam title in style, overwhelming Spaniard Albert Ramos-Vinolas to reach the US Open second round.
Tsitsipas, who entered the first Grand Slam of the COVID-19 era fresh off a run to the semi-finals of the tune-up event, never faced a breakpoint and broke Ramos-Vinolas seven times during the 98-minute 6-2 6-1 6-1 victory.
Tsitsipas, 22, who has never progressed beyond the second round of the US Open, entered this week with 16 wins to his name this season and has been tipped to make a deep run in a tournament missing several top players.
Tsitsipas broke to go ahead 3-1 and that opened up his game, as he went on to play the rest of the contest on his terms.
The loss brought a speedy end to Ramos-Vinolas's return to competition, as the Spaniard withdrew from last week's tune-up to attend the birth of his first child.
Despite taking the first two sets, Argentinian ninth seed Diego Schwartzman was knocked out in the first round by NZ-born Brit Cameron Norrie, who won 3-6 4-6 6-2 6-1 7-5 in a marathon encounter that lasted nearly four hours.
Both players served poorly with more than 50 break points in the match, but Norrie smashed 39 winners and saved two match points in the deciding set to claim his biggest Grand Slam win.
Seventh seed David Goffin fought off a spirited challenge from big-serving American Reilly Opelka to secure a 7-6(2) 3-6 6-1 6-4 victory in the opening round.
Germany's fifth seed Alexander Zverev got through a tricky first-round encounter against 2017 finalist Kevin Anderson in four sets, winning 7-6(2) 5-7 6-3 7-5 to move into the second round.
Anderson fired 20 aces to Zverev's 18 in the battle of the big servers, but the South African, who returned to the tour after a series of injuries, had no answer to the German's groundstrokes.
Serbian Dusan Lajovic, seeded 18th, became the first major casualty of the opening round, suffering a shock 6-1 4-6 6-4 6-4 defeat by Egor Gerasimov of Belarus.