London 2012: Triathlete Alistair Brownlee feared missing Games

World champion Alistair Brownlee admits he considered retiring '50 times' during the injury rehabilitation which followed an Achilles tear in February.

The 24-year-old competes in his first World Series event of the year in Kitzbühel, Austria on Sunday and says recovery has been tough.

"It's been really frustrating," Brownlee told BBC Sport.

"There were times when I wondered if it was ever going to get better and be able to race or train properly again."

Just two weeks ago, alongside his brother Jonny, he claimed a joint victory in his comeback race in Blenheim and was relieved to come through unscathed.

"I was a bit nervous really about the little things that could go wrong," said Alistair.

"I've done four-six weeks of solid training without feeling anything but you're never quite sure until you actually race.

"It felt absolutely fine to be honest so I'm happy with that."

World sprint triathlon champion Jonny, who has won World Series events in San Diego and Madrid so far in 2012, says it has been difficult to see his brother suffer during the crucial build-up to this summer's Games.

"He found it tough because he's had injuries before where when you recover, you don't feel them again, but the Achilles is something that kind of hung around," Jonny Brownlee told BBC Sport.

"He'd be running along in training and go over on his ankle and say 'that's it I'm retiring' and I'm like, 'what do I say? I'll keep quiet'. Then we'd run a but more and he'd say he was retiring again.

"We can joke about it now but it was tough seeing Alastair like that."

Alistair's physiotherapist Emma Deakin suggested in March that the triathlete could come back stronger than before his injury, but he confesses this may not be the case.

"I think that's a bit of an optimistic way of looking at it," said Alistair. "I missed three months of training which is never going to be ideal, three months out from an Olympic Games.

"But it could happen, the Olympic year is a funny year.

"I've got no chance of over-doing it because I've only been training for six weeks so that's probably the only positive you can take from it."

After competing in Kitzbühel on Sunday, the Brownlees will head to St. Moritz, Switzerland for a four-week training camp.

"As far as time is concerned, I'm not massively away [from where I want to be]," added Alistair.

"In the time I have left [before the Games] I could probably go from being completely unfit to fairly fit, so I'm hoping that if I have a good injury-free few weeks then it should work out well for me."

The brothers will return to the UK just over two weeks before the Olympic Games begin and after a 'rest' period in Leeds, will travel to London, four days ahead of the men's triathlon in Hyde Park on 7 August.