Dai Greene was hoping for some relay redemption after missing out on an Olympic 400 metres hurdles medal.
The world champion and team captain had to settle for fourth place, fatigue catching up with him as was not quite strong enough to come through at the finish.
The Welshman, the Britain's athletics team captain, clocked 48.24 seconds, 0.14secs off a medal, as he failed to complete the full set of major championship titles.
Greene's preparations have been hampered by injury and illness, but was still seen as one of Britain's leading medal prospects going into the Games.
Those problems appeared to catch up with him through the three rounds, though, his time well of Felix Sanchez's winning clocking of 47.63s.
"At the start of the race you know you are a bit tired, you give everything but when you come round the top bend you are really hurting," he said.
"Any mistake you make is magnified. I was still coming back strongly, just perhaps not as strongly as I have been in a one-off race.
"That's certainly to do with the rounds which took a bit too much out of me. Considering I was fourth in the semi-final, I was fourth tonight and beat some good guys. I was pleased with the way I conducted myself."
Looking ahead to the 4x400m relay, he added: "I'll be available. I'm on my recovery shakes and I'll be going about my business as professionally as I can and make myself available for the squad."