Jamaican 100 metres world record holder Asafa Powell is not the world's best sprinter, retired 200 and 400 record holder Michael Johnson said.
That honour, he said, goes to American world champion Tyson Gay.
"I measure sprinters based on consistency and (Gay) is the more consistent," Johnson said during an online chat on the International Association of Athletics Federations (IAAF) web site (www.iaaf.org).
"He's got better performances at championships," Johnson added of Gay, the world 100 and 200 metres champion.
"Asafa Powell is a great talent but he can never get it done. He's failed time after time at the championships."
Powell's world record of 9.74 seconds is a 10th of a second faster than Gay's best of 9.84 but the Jamaican has never won a global sprint title.
That will not change in Beijing, according to Johnson.
Asked by an online questioner how Powell could win 100 metres gold at the Beijing Games in August, Johnson replied jokingly: "Trip Tyson Gay."
He made the comment before Powell's manager announced the Jamaican would not compete again until late June because of a pulled pectoral muscle.
Johnson also predicted Gay would win the 200 in Beijing to match his 2007 world championship sprint double.
Gay will test his 200 metres speed for the first time this season on Saturday at the Jamaican International meeting in Kingston.
Gay also has talked of trying for Olympic gold in both the 4x100 metres and 4x400 metres relays, but Johnson said the latter would not happen.
"Tyson is very talented but there is no way he can make the US 4 x 4 (team)," Johnson said.
Other predictions by Johnson:
* American Jeremy Wariner, who Johnson manages, will win the Beijing 400 metres and some day break Johnson's world record of 43.18 seconds.
* Ethiopian world record holder Haile Gebrselassie will change his mind and run the Olympic marathon.
* Sweden's Susanna Kallur will defeat two-times US world champion Michelle Perry for the women's 100 meters hurdles gold medal.
* World 200 metres champion Allyson Felix of the US can become better than 1996 French Olympic 200/400 metres gold medallist Marie-Jose Perec. (The Beijing schedule rules out that double at August's Games).
* Merlene Ottey, the Jamaican-born Slovenian, will make her eighth Olympics at age 48. "Her career has been amazing," Johnson said. "She's an example of a real hero in the sport."
Johnson, an IAAF ambassador and president of a performance centre in his native Texas, also spoke favourably of the long-time success of Jamaican sprinting.
"Part of it is just tradition," he said in response to a question, "but they also start very early teaching good skills for sprinters."
Despite his nine world titles and five Olympic gold medals, Johnson has no inclination to coach.
"I'm not interested in coaching," he said. "It takes a special talent that I don't have."
