Eugenie Bouchard out of the US Open after suffering a concussion Friday night

NEW YORK – As Genie Bouchard slowly walked from the parking lot into Arthur Ashe Stadium Sunday afternoon, it was jarringly evident that something was wrong.

Bouchard’s hoodie was pulled over her head. She wore dark glasses, looked straight down at the pavement and moved very slowly, although she was walking unaided.

A short while later came the official word. Diagnosed with a concussion after a freak fall Friday night in the players’ locker room, the Canadian tennis star pulled out of the US Open a few hours before she was to play Italian veteran Roberta Vinci for a spot in the singles quarterfinals.

Saturday, the day after the accident and after she went to the hospital emergency room to be examined late on Friday, she withdrew from both the women’s doubles and the mixed doubles.

It’s a tough blow at any time, made even more unfortunate by the fact that after a season of struggle, the 21-year-old from Montreal finally was getting her groove back at this US Open, fighting hard through her first three rounds of singles to make the round-of-16 and still alive in both the women’s doubles and mixed.

According to Bouchard’s representatives, here’s what happened.

After a long day on the courts, with a nearly three-hour, three-set win in singles over Dominika Cibulkova then a match tiebreak victory in her first-round mixed doubles with Aussie Nick Kyrgios, Bouchard requested an ice bath late Friday night, after her press obligations were completed.

That was well after 11 p.m. To reach the ice-bath room from the locker room, players have to go through the training room.

At that hour, everyone was gone, and the room was pitch-black. As well, the floors had been cleaned and treated and were very oily.

A bit disoriented in the darkness, Bouchard slipped and fell on the floor – backwards – hit her elbow and then the back of her head quite severely.

She was examined by the medical staff at the tournament, then went to the hospital late that night but the classic symptoms of a concussion were nearly all in evidence: no vomiting, but migraine headaches the last two days, extreme sensitivity to light and sound, a very sore neck, and some dizziness.

Bouchard finally arrived on site at the tournament, as speculation swirled about her physical condition.

Some of the Canadian media had been outside near the entrance all afternoon. Just about every Canadian still in the tournament or about to compete walked by at some point – but not Bouchard. Until finally, at 3:36 p.m., she appeared and headed inside to be evaluated again by the medical staff.

Here's what it looked like:

There are no degrees of concussion, the doctor explained to her. You have one or you don’t (there are different classifications, though). Still, Bouchard reportedly still wanted to try to play Sunday, even talked about getting up on the treadmill and move, her representatives said. She arrived in practice clothes; two court reservations were made, then cancelled before the final word came down shortly before 4:30 p.m.

Unlike in team sports, where a team physician would make the decision on whether or not a player was fit to play, it would seem that in tennis – an individual sport without the same type of infrastructure – it is ultimately the player’s decision.

That might be technically true, with the player getting the relevant advice and then making a decision on whether or not to try to play. But players want to play; the Grand Slams do have a final avenue of discretion should it be a severe situation.

Tournament spokesman Chris Widmaier told Eh Game that the tournament referee and Grand Slam supervisor can rule that a player is unable to compete, in essence overruling the player, although that's a power that, according to the Grand Slam rule book, should be used judiciously. He added that in this case, it didn't come to that.

Bouchard, after listening to the doctor and those close to her, clearly made the right decision; there is precedent at the US Open to cause concern for what might have happened if she did take the court.

Almost five years ago to the day here, former No. 1 Victoria Azarenka went to play her second-round match against the Argentine Gisela Dulko with what she thought was only a headache, after an almost equally bizarre mishap in which she tripped on the edge of her sweatpants while warming up and ended up falling and hitting her head.

Azarenka took the court anyway, and had to retire from the match after she fainted, and was taken off court in a wheelchair.

The Bouchard renaissance that began with such promise in New York has now been stopped dead in its tracks for the time being. And there certainly will be more questions to come.

For example, was Bouchard alone when this happened? If so, why was she? Clearly exhausted even after the singles, the told the crowd during the on-court interview that she “couldn’t feel her body”. Then she went out to play even more tennis.

If she wasn’t alone, why didn’t someone turn on the light as she made her way through an unfamiliar room she sees only once a year? And why was that area not staffed?

Spokesman Widmaier said he couldn't comment to Eh Game about the various issues raised here, including the tournament's liability for this type of incident, because all the facts had not yet been gathered.

But one thing is certain; the incident could well compromise the end of Bouchard's season. She is scheduled for four more tournaments in Asia from the middle of September to the middle of October.

After the incident in New York, Azarenka was back within a month for tournaments in Asia and Russia as she made a big push and was the last player to qualify in the top eight for the WTA Tour championships, held that year in Qatar. But it took her awhile to fully shake off the effects – and it wasn't nearly as severe when it happened as the Bouchard situation was.