Sprint king Usain Bolt has not yet reached his peak and can lower his world records in the 100 and 200 metres if he has a rival to push him, according to former world champion Frank Fredericks.
The peerless Jamaican set his world marks of 9.58 and 19.19 at the Berlin world championships in 2009 with his best since then the 9.63 and 19.32 he clocked in London's Olympic stadium at last year's Games.
Namibian Fredericks, Olympic 100 and 200 silver medallist in 1992 and 1996, believes Bolt, who will turn 27 on Aug. 21, has it in him to stun the world again.
"He's still got two years according to my calendar - 28 was my peak - though I ran to 37 and ran 10.13 at 37," IAAF council member Fredericks told a Moscow news conference on Wednesday.
"I believe he can go faster at 200.
"With the 100 there are so many factors. You need a two metre tailwind, a perfect start... he's a big guy but if he pushes himself maybe he could go faster."
Bolt's lanky frame means he often starts a race slowly, a fact emphasised at the Diamond League meeting in London late last month when, despite clocking a season's best 9.85, he conceded his start had been so poor that in a stronger field he would "probably be fifth or something".
Bolt infamously false started and was disqualified from the world 100 final in Daegu, South Korea two years ago and in the absence of injured compatriot Yohan Blake - who took world 100 gold in 2011 - and suspended American Tyson Gay, is almost certain to reclaim his crown in Moscow on Sunday.
Fredericks questioned whether, with Blake's season hit by injury, Bolt had a serious rival to push him to greater feats - with his chief threat to double sprint gold in Moscow coming from former Olympic champion Justin Gatlin.
"Usain needs someone to push him and with training partner (Blake) injured - can he push himself?," Fredericks asked.
Then answering his own question, the bespectacled Fredericks continued: "But when he broke my record in Oslo he showed that he could."
Bolt ran 19.79 seconds for the 200 at the Bislett Stadium in the Norwegian capital on June 13, breaking Fredericks' 17-year-old stadium record by three hundredths of a second.
On July 6 the Jamaican then clocked 19.73 in Paris, the leading time this year.
The Jamaican, by his own admission "race rusty" after being dogged by a hamstring injury in the early part of the season, appears to have run himself into the shape where he could perhaps threaten in Moscow to at least get close to his world records, particularly on the fast Mondo track at the Luznikhi stadium.