"I think her acceleration is (still) there, " said Greene of the triple Olympic champion, who is struggling with her sprinting on her return to competition after taking last year off to have a baby.

"It just depends on when she gets to it (her acceleration). I think she gets to it too early. You can see her make a move, but she can't. Maybe she's not strong enough to hold it."

Greene said he had also noticed a difference in the running style of Jones, who has changed coaches since the 2002 season.

"I don't know whether it is because she has had a baby but her running style has changed. She has a lot more movement than she had before."

Such movement can lead to a waste of energy, Greene said, adding Jones's foot placement on the track appeared to be different.

"You see her stepping out in front of herself, rather than up under the centre of her body, which gives her a breaking force," Greene said.

Greene, who lost his 100 metres world record to Jones's partner Tim Montgomery, also knows these may be stressful times for Jones.

The winner of five gold medals at the 2000 Sydney Olympics is under scrutiny by the U.S. Anti-Doping Agency (USADA) although she has never failed a doping test and has denied taking performance-enhancing drugs.

"They haven't charged her with any thing," said Greene. "So why do people try to put her in that situation? I can't even put her in that situation."

She will attempt to qualify for the U.S. Olympic team in the 100 and 200 metres and long jump beginning with the 100 preliminaries on Friday.

Her best event this year may be the long jump after years of being the world's best female sprinter.

"It just takes one time for you to get beat," said Greene of Jones, who finished fifth in her last 100 metres race.

"Now all the women are like, oh, 'let's get her.' Now we get to see how tough she really is.

"Anybody can be a great athlete. What puts an outstanding, great athlete on the top is to see how they come back from a loss."