Kingstson: Back-to-back defeats for Usain Bolt have set tongues wagging about a possible change of guard at the top at the upcoming London Olympics, but the sprint double world record holder seems hardly worried by the chatter.

Before last weekend, the 25-year-old had not been beaten even once in four years - bar a disqualification for a false start once - but left the Jamaica Olympic trials with two defeats in three days, after twice faltering before training partner Yohan Blake.

Bolt remained positive ahead of the Olympics starting July 27, and was insistent he could turn around his form in time, reports Caribbean Media Corporation.

"I'm the Olympic champion. I have to show the world I'm the best. I can come back," he said.

"It's not like I was blown away or anything. So now, I know what I need to do to get it right."

Blake stunned Bolt for the first time last Friday night, clocking a world-leading 9.75 seconds to win the 100 metres.

Bolt recovered from a terrible start to finish second in 9.86 seconds.

Blake, the 100 metres World champion, returned Sunday night to shock Bolt for the second time, clocking another world-leading time of 19.80 seconds to win the 200 metres.

Bolt was relegated to second in 19.83.

He remains the favourite going into the London Games but pundits are already eyeing Blake as the man who could make the headlines at the July 27-August 12 world athletics showpiece.

Despite last weekend developments, Bolt said he would not be changing his preparation.

"I never train for one person. Everyone is talking about Yohan Blake and he is proving himself as one of the greatest," said the reigning Olympic champion in both 100m and 200m.

"But for me, it's going back to training, getting back to work and getting done what I've got to get done." (IANS)