John Isner had just reached the third round of the US Open for a fifth year in a row, but he was far from happy. The Flushing Meadows crowd had spent the latter part of his match cheering on his French opponent, Gael Monfils, and the American questioned what he perceived to be a lack of patriotism.
His irritation was understandable, to a point. Encouraging an opponent is one thing, but having your own double faults cheered? That has got to hurt.
"I was a little bit disappointed in that, actually. Not going to sugarcoat it," he said after his four-set win last week. "If I was playing in France, it certainly wouldn't be like that."
The Roland Garros crowd in Paris can indeed be one of the most partisan in the world when a Frenchman is in action. In Britain, few occasions bring out unabashed nationalistic fervour, apart from royal weddings, more than an appearance by native son Andy Murray (or previously, Tim Henman) at Wimbledon.
The New York crowds, however, can be the noisiest of all. Alternately biased to their own, and incredibly generous to any foreigner who displays skill and guts on the court - and Monfils showed both.
They have in the past shown rabid support to home players like Pete Sampras, Andre Agassi, John McEnroe and Jimmy Connors. The Arthur Ashe and Louis Armstrong stadiums are no strangers to chants of "USA, USA, USA". It has lifted many a flagging American spirit.
"This is the only grand slam in my career that I've never missed," Agassi said last year at Arthur Ashe Stadium, during his induction to the Court of Champions. "The reason, quite honestly, is you ... I miss your sounds. I miss your silence. I miss giving you everything I had and a little bit more."
Great if those sounds are cheers for you. Not so great if they are against you, as Isner experienced.
Not surprisingly, considering the fallout, the crowd made a point of backing Isner in his next match and he acknowledged their support on more than one occasion. Unfortunately, he went down to Philipp Kohlschreiber of Germany in four sets.
Should Isner have expected the crowd's unconditional support in the first place? Is it a matter of patriotic duty? Is home support a right you should expect, or a privilege you earn?
Perhaps a more pertinent question is that in individual sports, should the individual's nationality matter?
Flag waving, some will feel, is best left to the World Cup, the Ashes and the Olympics.
Like golf's Ryder Cup - "team" tennis has the Davis Cup for that, anyway. Anyone lucky to have witnessed the 1987 clash between the US and West Germany - in particular Boris Becker's six-and-half-hour epic against McEnroe - will attest to how patriotic the American crowds can be.
But athletes these days are global brands that transcend increasingly blurred geographical divides. Roger Federer, Usain Bolt and Lionel Messi are idolised far beyond the borders of their native lands.
At No 17 in the world, Isner is the highest-ranked American player on the ATP Tour. He is an emerging talent, so maybe if he had a higher profile, crowds would develop more of an affinity for him.
Isner, in fact, is the only American in the world top 30. He and the other Americans at this year's US Open are not in the same class, nor do they command the popularity, of crowd favourites such as Roger Federer, Rafael Nadal, Novak Djokovic or Murray.
Perhaps what upset Isner most is that the crowd simply saw Monfils, at No 39, as the more exciting prospect, not to mention the underdog. Either way, a lack of patriotism does not come into it.
Maybe the American fans had a premonition: For the first time since the event was founded in 1881, no American male made it to the round of 16.
So, then, it is to the credit of New York's noisy tennis fans that they will continue to show up and channel their support toward whoever is left in the draw.
Wherever they come from.
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