Tim Brabants ended the canoe sprint men's 1000m K1 final in eighth place as Norway's Eirik Veras Larsen won gold.
Brabants, who came in to the Games struggling for full fitness following a serious tendon injury, could never contest the lead at Eton Dorney.
Drawn in lane one nearest the grandstand, the 35-year-old had the support of the home crowd but fell well behind Canada's Van Koeverden as he surged in to an early lead. But with 250 metres to go in the individual 1000 metre kayak sprint, Larsen edged in to first place to claim gold.
World champion Adam van Koeverden finished second to claim silver, while Max Hoff from Germany won the bronze.
Speaking to reporters afterwards, Brabants said he felt good in his warm up but was disappointed with the result. He said: "Unfortunately the other guys were better. Everybody in that final has been in a final this year, at the world cup and the Europeans, except me.
"To be in the final was my main aim and then to try and make that podium again. I felt like I could. In the warm up I felt strong but unfortunately I felt like I was never in the race for some reason. The conditions weren't bad. I am not making excuses at all. I would rather not have had lane one but it didn't make a difference on the day.
"The right guys won and they showed their class, they showed their form. My main problem is letting down the home crowd. I wanted to add to the medal tally for Team GB like all the other athletes and especially like the returning gold medallists from Beijing who have done so."
Asked whether he intended to continue, the accident and emergency doctor said he would return to his day job, probably at Nottingham's Queen's Medical Centre, in the next few weeks but seemed to rule out competing in Rio in four years.
He added: "I don't want to give up just yet. We work on four-year cycles. This is the end of one cycle and so in a few weeks time we will reassess where we are. I love the sport. I love being in this environment, so I certainly don't want to stop just yet."
In the women's K4 500m, Jess Walker, Angela Hannah, Rachel Cawthorn and Louisa Sawers finished fifth with Hungary taking gold.