Are Usain Bolt's best days behind him? Sprint legend's toils suggest trouble ahead

The superstar athlete was pushed all the way, looking pained and awkward as he did so, and barely won the race in a sluggish 20.29 seconds on a warm, windy day at Randall's Island - the time over a second slower than his world record of 19.19 at the distance.

Bolt was running into a stiff headwind of 2.8 metres per second that affected his time to a degree - but the slender margin of victory against a relatively weak field was more telling than the time on the clock, and the six-times Olympic gold medal winner admitted that he was bewildered by his sub-standard turn.

The 28-year-old Jamaican, who also holds the world record in the 100 metres, failed to show his legendary runaway burst of speed and only just held off second-placed Zharnel Hughes of Anguilla, who timed 20.32.

"I'm not happy about my performance today. My turn was horrible, I don't know what happened," Bolt said. "My worst turn ever."

Bolt said the turn affected the rest of his race, run in front of a packed grandstand filled with fans from his homeland.

"After I came off the turn, I knew it wasn't going to be fast ... so I pretty much just wanted to get home. I didn't really stress it too much."

He had hoped to break 20 seconds in the race as he aimed to build towards this year's Beijing world championships in August after a 2014 season limited by injuries.

It's not the first poor showing for the hero of London 2012 and Beijing 2008: Bolt managed just 20.20 in Kingston and 20.13 in Ostrava earlier this year.

In other featured races in the Diamond League meet, world record holder David Rudisha of Kenya, who pulled up early in his last race, ran easily in winning the 800 metres in 1:43.59, three-hundredths of a second shy of the year's best.

Cuban triple jumper Pedro Pablo Pichardo, whose 18.08m in Havana was third longest ever, won with 17.56 ahead of American Olympic silver medalist Will Claye with 16.96.

Tyson Gay overcame a slow start to win the men's 100 metres in 10.12 seconds, straining to overtake Jamaican Nesta Carter, second in 10.15.

Like Bolt, his time was hardly stellar - but taking into account the 1.7m/s headwind it was still a solid performance.

"My start wasn't great and I feel bad because we've been working on it," said former double world champion Gay, striving to find top form after serving a one-year doping suspension.

"I ran like poop in the meet, so I'm still working on it."

Fabiana Murer of Brazil, pointing towards next year's Rio Olympics, repeated her New York victory of a year ago by winning a high-calibre women's pole vault by clearing 4.80 metres with fewer misses than Nikoleta Kyriakopoulou, of Greece.

Olympic champion Jenn Suhr was third at 4.54.

American Francena McCorory set a world-leading time of 49.86 seconds in winning the women's 400 metres.

When he burst onto the scene at Beijing in 2008, Bolt seemed truly superhuman, jogging his way to gold in both 100m and 200m.

A year later, when he smashed his own 100m and 200m world records at the 2009 World Championships in Berlin, he ran in a manner which made us think he could never be beaten with marks of 9.58s and 19.19s.

He turned 23 during that championships in Germany, still young for a sprinter, and at the time it seemed that he could beat the 9.50s mark for the 100m and possibly even the 19.00s mark in the 200m. No prediction seemed too outlandish.

Yet while he has remained the best in the world, he has never since reached the heights he did in those heady days of August six years ago. Injuries were not kind to him in 2014, and with the competition - an in particular Justin Gatlin - looking in good form this season, all the signs suggest that Bolt's best days are long behind him.

The unthinkable now seems not just possible but probable: Bolt could well lose one of his crowns at the World Championships later this summer. That the fall from grace is set to happen at the same Bird's Nest Stadium in Beijing where he first became a legend will only add to the poignancy.