MOSCOW -- The ever entertaining and always amusing Usain Bolt will soon be blazing down his lane to give track a dose of positive -- from performances, for a change, and not tests.

The recent doping scandals involving Tyson Gay and Asafa Powell have cast a dark cloud over the sport, one that Bolt's hoping to blow away by sprinting his way to gold.

That Gay or Powell, or even an injured Yohan Blake, aren't at the world championships that open Saturday doesn't really overshadow the event because anytime Bolt steps into the blocks, he alone, by himself, makes for compelling theatre.

When the charismatic Jamaican is in top form, and properly motivated, records can be broken.

And track could certainly use that at the moment, given that Gay, Powell, Sherone Simpson and Veronica Campbell-Brown have all recently tested positive for banned substances.

Granted, there aren't as many threats to Bolt in the 100 metres with Blake, his top rival and the defending champion, also sidelined due to a nagging hamstring injury. But these days Bolt's biggest challenger may just be the clock anyway.

"After the 2012 Olympics, I was telling people who weren't into track and field, 'Hold onto your popcorn because next year is going to be even more exciting. We're going to have the same people,"' American sprinter Justin Gatlin said. "Never in a million years would I think it would end up like this. I still think it's going to be exciting."

Indeed, largely due to Bolt's popularity. It's not like he won't be pushed, though.

After all, Gatlin beat him in Rome two months ago and is eager to prove that it wasn't a fluke, that he's closing the gap on the world-record holder.

These two aren't exactly best of friends. They don't really talk all that much off the track, but there's definitely a measure of respect. Hard not to respect the sprinter who has captured six Olympic titles and shattered world records in the 100 (his current mark is 9.58 seconds) and the 200 (19.19).

"He's done so much for the sport and in the sport," Gatlin said. "People either want to see Bolt get beat or don't want to see him lose. There's pressure of always being perfect."

Blake fleetingly stole Bolt's stage last year by beating his teammate in the 100 and 200 at the Olympic trials and by winning the world 100 title in 2011 when Bolt false-started.

Had Blake been healthy, this would've been a good rematch. Gay would have been a worthy opponent, too, especially since he was healthy for the first time in quite a while. But the American, who won the 100 and 200 at nationals, failed an out-of-competition doping test.

Powell won't be here, either, after testing positive -- along with Simpson -- for a banned stimulant.

"I want to line up against Yohan. I want to line up against Tyson. I want to line up against Asafa," Gatlin said. "This kind of takes a spark out of it a little bit."

He paused, contemplating his impending showdown with Bolt.

"But now it's like a real heavyweight bout, where you have two guys who aren't the best of friends, ready to run against each other and rumble," Gatlin said.

Lately, Bolt has been the undisputed champion, captivating the crowd with his bravado and clowning around. When the gun sounds, he's all business for less than 10 seconds before returning to his light-hearted ways.

This race, with the final on Sunday, has his full attention. He's not overlooking anything -- or anyone.

"I am fit and ready to go!" Bolt wrote in a recent email. "Right now my only focus is winning three gold medals at worlds."

Besides the 100, there are other intriguing plot lines at the worlds:

-- Two-time Olympic pole vault champion Yelena Isinbayeva of Russia wrapping up her career after the meet.

-- Trey Hardee attempting to defend his world title against Olympic champion and world-record holder Ashton Eaton.

-- Mo Farah trying to capture the 5,000 and 10,000 by holding off training partner Galen Rupp.

Of course, anytime Bolt steps on the track, whether it's in the prelims or the final or even for a curtain call, he is the star attraction.

"He realized what value he still adds to the sport. He realizes what an icon he is for us," former sprinter Frank Fredericks said. "This is how he makes his living. I hope he continues to sprint and sees how far he can push his body.

"I hope he can push it a bit farther."