(CNN) -- As a pained Rafael Nadal collapsed in front of a shocked press conference in New York on Sunday, it seemed for a moment as if the U.S. Open was about to claim its most high-profile casualty.
It sparked fears that Nadal -- a 10-time grand slam winner -- would be forced to abandon the defense of the title he won at Flushing Meadows last year and become the 19th player to pull out of the season's final major.
Thankfully, Nadal's seizure was quickly diagnosed as cramp, and he later posted a video on his Facebook page reassuring fans he was fine.
But the episode once again highlighted the huge demands placed on top level athletes in the sport.
In the women's game, former champions Kim Clijsters and Venus Williams were forced to pull out of the tournament, while in the men's draw world number six Robin Soderling was notable by his absence.
After Marcel Granollers and ninth seed Tomas Berdych retired from their respective third round games on Saturday, a total of 10 male players had quit mid-match.
The record number of retirements in the Open era has been even more curious given that temperatures in the Big Apple have been lower than in recent, sweltering years.
It has led many people to question whether the stars of the game are close to burn out; playing too many games in a packed Tour schedule which boasts 62 events on the men's side alone.
Even the players themselves are hinting as much.
World number four Andy Murray took to Twitter to say: "Is the 18th pull out in the us open (sic) telling the tennis authorities anything?? No?? Thought not...."
Serbia's Janko Tipsarevic, who made the fourth round after Czech opponent Berdych retired in the second set, was quoted by USA Today as saying: "The season is too long, that's the only answer."
Even Roger Federer, a veteran of the ATP Tour and a man with 16 grand slam titles to his name, was taken aback at the amount of players who have been forced to throw in the towel.
He told a press conference: "For me it is shocking to see so many retirements. I'd say 50% of them are unlucky because they're not feeling well or getting injured or carrying an injury.
"It comes out in best-of-five-set tennis. You can't hide it, in my opinion. Could some guys finish the matches? I'm sure, but they didn't decide to.
"For me, it doesn't matter how bad I'm feeling, I will be out there and giving it a try, because you never know what's going to happen. Every player feels different. It's unfortunate it happens for the fans, I guess."
Several explanations have been offered -- that players are willing to push the pain barrier for the season's last major tournament, or that the prizes on offer are too great for them to resist.
The ATP -- who run the men's tour -- insist withdrawals are down and that the number of events on the calendar has been reduced, with an extra two-week break in the off-season due to come into force next year.
They also urge against drawing strong conclusions from the unusual number of pull-outs at the U.S Open -- a tournament that operates outside the ATP's calendar.
But commentators like Kevin Mitchell, from British newspaper The Guardian, blame an overloaded schedule for a catalogue of niggles.
He claimed the number of recorded injuries in the men's game this season has now surpassed the 500 mark -- quoting figures from tennisinsight.com -- and said many players are putting their careers on the line by playing when unfit.
Though these figures are difficult to verify, Mitchell's sentiment rings true with many of the players.
A smiling Nadal conducted a second round of interviews after his bout of cramp to demonstrate he was just temporarily incapacitated, telling reporters: "It was just unfortunate that it happened in the front and back of my leg at once.
"It's just bad luck that it happened in public. It was really hot, I ran a lot and you sweat a lot in these conditions."
The Spaniard's challenge for the 2011 Wimbledon title was also dominated by an injury he picked up in a win over Juan Martin Del Potro, while world number one Novak Djokovic handed the Cincinnati Masters title to Murray last month after he retired with a shoulder injury.
The ATP's figures show walkovers and retirements have fallen for the past three seasons and they say electronic methods for assessing players' health have been introduced, but concerns persist about the demands placed on the game's stellar names.
With the best part of a week still to go in New York before the champions of 2011 are crowned, the guardians of the game must be hoping the on-court action dominates the headlines from now on.