By Nick Mulvenney
LONDON (Reuters) - Dayron Robles was outwardly confident of retaining his Olympic 110 metres hurdles title but, still struggling with the back complaint that wiped out his season, it sounded more like hope than expectation.
The 25-year-old Cuban, who holds the world record of 12.87 seconds, had just two outings at minor meetings early in the year and in London will be challenged by three rivals who have run sub-13 second times this year.
China's Liu Xiang, the 2004 Olympic champion, matched Robles's record mark in an illegal wind in Oregon in June, world champion Jason Richardson has run 12.98 twice and his fellow American Aries Merritt ran 12.93 three times in three weeks.
Robles, who lost his world title to Richardson last year when he was disqualified from the final for impeding Liu, conceded that circumstances were not as favourable as they were four years ago.
"In Beijing I was 21, I'd just beaten the world record, I'd run 10 or 12 races without losing any, I was in very good form that year," he told a news conference on Sunday.
"This year, I haven't competed, I have had few chances to compete."
His coach Santiago Antunez explained that the back complaint had always afflicted Robles.
"He's got a problem caused by his flat feet which gives him pains in his back and his buttocks," he told Reuters.
"They prevent him occasionally from doing certain drills so there are races in which he can't work at full pelt.
"They are complaints, not injuries, he can train with them but not at the highest level of competitive intensity."
Liu has also been training in pain for much of the last five years because of the Achilles injury that forced him retire in the heats of the Beijing Olympics.
With the two fastest high hurdlers of all time training through injury, world indoor champion Merritt, who transformed his hurdling after moving from eight to seven steps before the first hurdle, is being touted as favourite for gold.
"For myself, the biggest favourite is always going to be me," he said.
"This has been a great year for 110 hurdles because there have been some great athletes ... (but) anything can happen. Any of the eight guys that get into the final can win.
"I feel really good, I've evolved a lot and we'll find out the truth on August 8."
Robles has not run a sub-13 second time since 2008, the year he claimed the world record in Ostrava, and concedes he is likely to have to beat the high hurdles benchmark to win gold.
"I think it will take a run below 12.95 seconds to win the gold, I'm prepared to go below 13," he said.
Robles had said previously that London would be his last Olympics but, with his competition just a few days away, indicated he was having second thoughts.
"I want to think about overcoming this first obstacle, which is these Olympics," he said. "I have no idea what can happen afterwards. I will take some time and then decide."
(Additional reporting by Rex Gowar, editing by ....)