Daniel Awde was forced to withdraw from the decathlon with a knee injury after the second event, the long jump.
Awde had set a personal best of 10.71s in the 100m to lie seventh overall, but then committed two fouls in the long jump and already looked to be struggling before managing 6.83m with his final attempt.
"I've had a flare up of patella tendinitis and if I continued it would probably rupture," Awde said. "It's been a real rollercoaster ride. We try to find solutions to it. It works for about a week, find another solution and that works for about a week.
"If you spoke to me at the start of the year I wouldn't have expected to be here in the first place, it's been a real bane of my life for the last two years.
"I'm in the best shape of my life. I was so ready for this to put on a good show, entertain the crowd. I was ready but my knee wasn't. Without being too arrogant, if the pain is enough to make me stop and pull out of my home Olympics, then it's too painful."