British judoka Gemma Howell's Olympic hopes were ended in the first round of the -63kg category by France's world champion Gevrise Emane.
Howell had already been warned for passivity when a close decision went against her for an illegal leg wrap.
This "hansokumake" disqualification came after the referees had taken a long look at the video replay.
It was a cruel blow for Shropshire's Howell, who has fought back from two serious knee injuries.
"It was the right decision, I was down on penalties," said a deflated Howell afterwards.
"I tried a move but it didn't work.
Britain's Olympic judo history
- Kate Howey
is the last British Olympic judo medallist, having won silver at Sydney in 2000, eight years after a bronze at Barcelona in 1992
- Howey is the only British judoka to compete at four Olympics, and carried the GB flag at the opening ceremony in Athens in 2004
"I knew she was good; I had to be better."
The 22-year-old only started training again in March after nine months out recovering from surgery to the anterior cruciate ligament of her right knee.
But since then she has won four of the five competitions she entered, including the British Open in May.
So hopes of a first British medal in this sport since 2000 were not unreasonable, but Howell knew she would have to be at her very best to have any chance against Cameroon-born Emane.
The leg-wrap call was a close one, particularly as the rules have only recently changed, but if Howell is honest she will know that the world and European champion looked more dangerous for most of the contest.
The 30-year-old Emane has been at the top of the sport since 2005 but has actually enjoyed most of her success at the heavier weight category of -70kg, whereas Howell has spent most of her career fighting at -57kg, and the difference in power showed.
Howell will have learned much from this experience, though, and a clean run of fitness should see her back in contention in 2016.
"I don't have any positive thoughts right now, I'm gutted," she added.
"I'm happy to be here but I wanted a gold medal. I didn't come here to fight hard, I came here to win.
"But just watch this space, I'll be back."