Olympic and world champion Maurice Greene's time as the world's fastest man is over for good, according to five-times Games gold medallist Michael Johnson.

Despite surrendering his 100 metres world record to fellow-American Tim Montgomery last year, Greene predicts he will reclaim the mark this season.

But Johnson, world 200 and 400 record holder, believes Montgomery's record of 9.78 seconds will withstand all assaults this season.

"You have to look at it realistically, his (Greene's) career has been unbelievable, no guy stays on top that long in the 100 but...it's over," Johnson told Reuters on Tuesday. "Not that he still won't have some good races but it's over him dominating. I can't see it happening.

"He's going to have some fast races but he's not going to dominate anymore. Guys now realise he can be beat."

In his first race of the season in Eugene, Oregon at the weekend Greene finished third in 10.33 seconds.

But Greene, 28, was still satisfied with his effort predicting that he would reclaim his world record and win the 100 and 200 metres at the Paris world championships.

The showdown between Greene and Montgomery is expected to provide the highlight in Paris but Johnson does not see the showcase event ending in an American sweep of the top two places.

With Montgomery still searching for a full-time coach and his partner Marion Jones about to give birth to the couple's first child, Johnson believes he has too many distractions in his life.

"Montgomery and Green could very well not even medal at the world championships," said Johnson, who is in Monte Carlo for the Laureus Sports Awards. "Montgomery has a coaching crisis trying to find someone to coach him, Greene still isn't back to the form he was and may never get back there.

"I think we'd all be setting ourselves up for some huge disappointment to start talking about a huge showdown between Montgomery and Greene.

"I would actually bet against those two guys going gold and silver, I think there are other guys in there who can break it up.

"One of those guys might get a gold or a silver but they won't be one-two. And I don't see a world record this year.

"I think it's going to keep falling but probably next year. Most of the guys who are running well right now have other issues going on."