"Hopefully, I will be more healthy next year. Next year is my last year. I will try to compete in the world championships," said the 2004 Olympic champion and former world record holder.
Sebrle was the slowest of the decathletes in the opening discipline, the 100 metres, after a heel injury flared up.
His time of 11.54 was over a second down on American title favourite Ashton Eaton (10.35), who broke Sebrle's world record at the US trials in June.
"I could not run for the past 14 days," Sebrle said.
"But I expected it would be better in the Olympics because always in the Olympics you hope until last moment.
"The 100 metres was okay with the pain but not with the time," he added. "For the long jump, I couldn't run."
Sebrle, who has won every major title in the event, had six years on the next oldest competitor in the decathlon - Kazakhstan's Dmitry Karpov - and 13 on Eaton.
His longevity in an event that incorporates sprints, throws, and jumps before finishing with the decathletes dragging their weary bodies around the track for 1,500 metres, is remarkable.
Sebrle's world mark of 9,026 stood for 11 years until Eaton increased it by 13 points.
"It's really good," Sebrle said of the 24-year-old's record.
"The difference in his record and my record is just one centimetre in high jump. It's unbelievable.
"Of course I had the world record for 11 years. I won the Europeans and the worlds and Olympics and now it is time for another man," he added.
"I think he may put more points than 9,039 - but not today."
Asked what the highlight of his illustrious career was, Sebrle answered: "I have many memories. Of course I enjoyed my world record. When I ran the last metres and I saw the time it was a really good feeling.
"Second one, is I won the Olympic games in Athens. It was perfect and I enjoyed it."
American Eaton came into these Games as one of the hottest favourites for gold.
Eaton, 24, the 2011 world silver medallist, holds a 105-point lead over compatriot and world champion Trey Hardee after the opening three events, helped by a lifetime best throw of 15.48 metres in the shot.
"I feel good and my body feel good," he said. "It was a fantastic morning."