Rafael Nadal has revealed he is dealing with a wrist injury, putting his participation in the Laver Cup in doubt.
Nadal was the only member of Team Europe not to be selected for action on the opening day of the competition.
But his non selection was not thought to be related to any injury concerns.
However, as Nadal watched Stefanos Tsitsipas’ clash with Taylor Fritz from the sidelines, cameras captured the strapping on his left wrist.
The tape was still visible during the doubles match between Roger Federer and Alexander Zverev versus Jack Sock and Denis Shapovalov.
At the start of second set, the US Open champion was asked by Mark Petchey about the strapping and the Spaniard revealed he had an issue but was hopeful of still taking part.
He said: “Hopefully not. Let’s see tomorrow how things go.
“After New York, the body always feels down a little bit.
“Some issues can happen but here I am. I’m trying hard to be ready for when the team need me.
“Let’s see. All of the matches are very difficult.
“If I am not at 100 per cent, there is another player.
“But I am confident I can help.”
If Nadal is not able to play, he will be replaced by his compatriot Roberto Bautista Agut.
Nadal required treatment during US Open because of an arm problem.
The 19-time Grand Slam winner will hope his issue is not too serious as he seeks to close in on Novak Djokovic’s No 1 ranking.
After his latest success at Flushing Meadows, Nadal moved just 640 points behind his Serbian rival in the ATP rankings.