Paul Hession failed to advance to the semi-finals of the 200m after a fifth-place finish in his heat.
The Athenry athlete clocked a time of 20.69 which was outside his season's best, as Yohan Blake led home the runners in heat four in a time of 20.38.
Usain Bolt began his bid to add a second Olympic 200 metres crown to his two 100m titles with a hugely comfortable victory in the first of the heats in a time of 20.39.
After the race, pondered what might have been: “I had a good start but the middle section is where I seemed to lose it.
“When I ran my 20.54 in Lucerne I was quiet good in the middle section. I finished reasonably well but I was too far back .
"I would like to have beaten Serhiy Smelyk of the Ukraine who finished a place ahead of me, but it still might not have been enough. I would have got through in some of the other heats, but that is still not quick enough anyway.”