LONDON - With his contact lenses lying somewhere across the ring, American flyweight Rau'shee Warren trudged out of the London Games for the professional ranks on Friday with the ignominy of an eight-year Olympic losing streak.

The 25-year-old, the first American boxer to compete in three Olympics, lost a narrow decision 19-18 to Nordine Oubaali of France, who moved on to the quarter-finals and one victory away from securing at least a bronze.

"I thought I had the decision but overall you don't know what they are counting on the paper. It's a big disappointment you know coming a third time and then losing for a third time," Warren, head down and despondent, told reporters.

"As you can see this isn't my lane anymore, coming to the Olympics, just trying to get the gold and bring it back to the United States."

It did look like his lane, though, after a bright first round where he picked off the Frenchman to take a 9-7 lead. However, one of Oubaali's punches knocked Warren's contact lenses out and changed the course of the contest.

"The headgear... it kept falling down over my eyes, then my contacts fell out in the first round so I was having to wait for my opponent to get a little closer so I could throw my shots," Warren bemoaned.

"It always happens, even when I am training, when I have been hit and when the contacts come out it is really blurry."

TACTICAL ERROR

A costly tactical tweak after the first round also scuppered the American, who lost in the first round at Beijing after being misinformed about the score midway through his bout.

Instead of working the combinations that put him in front, his corner instructed him to hold back and look for the key blow.

Encouraging Oubaali, who started to beat the American to the punch, was not a wise move.

"I was just trying to flick the jab and just trying to deliver one shot instead of two, three or four shots but I guess that is what cost me the fight as he was just more aggressive and I was just trying to land my shots," Warren said.

"(We) have got to talk about getting something else, maybe a world title in the pros."