A seventh main draw US Open campaign has ended early for John Millman, with the former quarterfinalist exiting to qualifier Henri Laaksonen in the first round.
The world No.43 Australian has recently battled a toe injury and after landing awkwardly on his knee early in the first set, the challenge appeared to grow.
Entering with momentum after winning three matches to qualify, Laaksonen claimed his 7-6(2) 7-6(2) 6-1 in two hours and 28-minutes.
While it was a close encounter as the first two sets were decided in tiebreaks - the pair exchanging the only breaks of serve midway through the second set - Laaksonen took a 4-0 lead in the third set and didn't look back.
The world No.130 Laaksonen closed out victory with 16 aces and 33 winners overall. Millman, by comparison, struck three aces and 17 fewer winners than the Swiss.
He was one of five Australians in action on the opening day of play in New York.
James Duckworth is currently contesting his first-round match against Pedro Martinez of Spain, while Alexei Popyrin, Nick Kyrgios and Astra Sharma play their first-round matches later today.
> PREVIEW: US Open 2021 - Aussies in action on day one
Aussies in action - US Open
TODAY'S RESULTS
Men's singles, first round
[Q] Henri Laaksonen (SUI) d John Millman (AUS) 7-6(2) 7-6(2) 6-1
COMING UP
Men's singles, first round
James Duckworth (AUS) v Pedro Martinez (ESP)
Alexei Popyrin (AUS) v Radu Albot (MDA)
Nick Kyrgios (AUS) v [18] Roberto Bautista Agut (ESP)
[14] Alex de Minaur (AUS) v Taylor Fritz (AUS)
Jordan Thompson (AUS) v Gianluca Mager (ITA)
[WC] Max Purcell (AUS) v [13] Jannik Sinner (ITA)
Women's singles, first round
[Q] Astra Sharma (AUS) v [8] Barbora Krejcikova (CZE)
[1] Ash Barty (AUS) v Vera Zvonareva (RUS)
Ajla Tomljanovic (AUS) v [WC] Katie Volynets (USA)
Sam Stosur (AUS) v [28] Anett Kontaveit (EST)
[WC] Storm Sanders (AUS) v Misaki Doi (JPN)
> READ: US Open doubles draws revealed