Nick Kyrgios took a knee before his Laver Cup match against Roger Federer but denied the act was in support of American athletes' anti-Donald Trump protests.
The 22-year-old from Canberra was also in tears after the match but that was because of how close he came to a second career win over the Swiss master.
The Australian knelt for about three seconds at the net ahead of the pre-match warm-up before losing to Federer in a third-set tiebreak in Prague on Sunday.
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It sparked US media speculation he had chosen to engage in the intensifying spat between the country's sports world and Mr Trump, who has uninvited NBA champions Golden State from a White House visit.
Mr Trump earlier attacked protesting NFL players by suggesting anyone who took a knee during the national anthem was a "son of a bitch" and should lose their job.
Kyrgios, who made headlines in January when he wore an anti-Trump T-shirt, later in his post-Federer match press conference rebuffed claims he had joined in the protest.
"F**k no. Serious?" the Australian responded to the question from journalists.
"I'm doing that before most matches just to remember, you know, the two most important people that have passed away."
Kyrgios has lost a grandmother and grandfather in recent years.
The Australian, playing for Team World, had a match point but ended up losing to the 19-time grand slam winner Federer 4-6 7-6 (8-6) 11-9, with the Swiss star clinching the inaugural Laver Cup for Team Europe.
