Ireland's 1,500 metres runner Ciaran Ó Lionáird questioned whether he wanted to remain in the sport after finishing second last in his heat at the London Olympics.
The Cork runner is only 24 but, after finishing 10th in the World Championship final last year, he has struggled desperately with an Achilles injury in 2012.
And he admitted he would have no hesitation in giving up if he felt he could not get back among the world’s best.
Ó Lionáird clocked three minutes and 48.35 seconds tonight, the fact it was a season’s best an indication of how little he has raced this summer.
“I wanted to call the year over back in May, but all the people around me said, ’No, it’s the Olympics, see what you can do’,” said Ó Lionáird , who moved to Portland, Oregon, last autumn to train briefly alongside the likes of Mo Farah before changing base again in the spring to Eugene.
“I am not where I was last year. My Achilles still hurts day in and day out.
“I try to manage it the best I can, but that track is rock hard. I need to go away and re-evaluate and see if I can get better.
“It was a futile effort. I made the decision to do it so I gave what I had today and I didn’t have a lot.
“I really did after 10th place last year think to myself, ’What do I need to do to get a medal?’.
“I could have consolidated and kept building on what I did, but I really tried to shoot to be the best in the world and that sent me crashing.
“I just have to think if I can become the best in the world because if I can’t then I don’t intend doing this.
“I was 10th in the world, I am not going to hang around for the next four years to be the same. It seems stupid to say that coming next to last in the prelim, but that’s all I am here for.
“I could move on tomorrow and be perfectly fine with it if I knew I couldn’t do it.”
There was better news for Joanne Cuddihy, who qualified for the semi-finals of the 400m as a fastest loser.
The 28-year-old finished fourth in her heat in 52.09secs, but it proved enough to progress.
Cuddihy was still not impressed with her run, though.
“The crowd was electric, the best I’ve ever experienced,” she said. “I think I let the occasion get to me.
“I went out fast – that was the plan – and it was only when I got in the home straight that I realised I didn’t have the legs for the finish.”
Fionnuala Britton finished 15th in the 10,000m final, running 31:46.71.