The World Athletics Championships will begin with a bang in Beijing this weekend with what promises to be one of the most high-profile battles for men’s 100 meters gold in recent memory.

There is enough to intrigue purely on the track, where the biggest star in athletics, Usain Bolt, will face arguably the greatest challenge to the dominance he began in the 2008 Olympics at the same Bird’s Nest stadium where this week’s championships will take place. At the age of 33, 2004 Olympic and 2005 World Championships gold medalist Justin Gatlin is the form of his life and has run the fastest time in the world this year, with a personal best of 9.76 seconds.

But it is the subplot to the showdown that has added extra spice to the anticipated showdown. While Bolt has long been seen as the ultimate symbol that greatness can be achieved without the aid of performance-enhancing drugs, which have so tainted the sport of track and field, his rival has twice been suspended for doping. In 2006 the American was handed an eight-year ban, later reduced to four on appeal, for testing positive for testosterone. That Gatlin’s coach was Trevor Graham, infamous for guiding Marion Jones, among other drug-tainted athletes, only further tarnished his reputation, despite Graham’s claim that Gatlin has been sabotaged by a masseuse rubbing testosterone cream into his legs.

Since returning to the sport in 2010, Gatlin has increasingly gotten back to and then surpassed his previous best. But that he has done it an age when most sprinters are slowing down has raised further suspicion. Some say even if he is no longer doping, he is benefiting from the steroids that have been shown to have long-lasting effects. His supporters, though, state that it is precisely his forced hiatus from the sport that means his body has the freshness to defy traditional timelines.

That the battle between the two comes at a time when athletics is embroiled in one of its most damaging drug scandals yet has only added to the attention on it. Earlier this month, a report in Britain’s Sunday Times newspaper and on German broadcaster ARD claimed that a third of medals in endurance events at the Olympics and World Championships between 2001 and 2012 were won by athletes who recorded suspicious tests. Meanwhile, it was later revealed that 28 athletes were suspended for doping offenses at the 2005 and 1007 World Championships.

To many, Bolt, now more than ever, needs to save the sport from the drugs cheats, personified by Gatlin. The man elected as the new president of the sport’s governing body, the International Association of Athletics Federations (IAAF), Sebastian Coe, has said that the thought of Gatlin crossing the line in first place and getting the gold medal placed round his neck makes him “queasy.”

The two men involved, though, have both tried to play down the stakes involved. While Gatlin has said that he doesn’t care if he’s portrayed as the bad guy, Bolt has been keen to shake off the tag of the sport’s savior.

“I can't do this by myself, it's never going to be one single person, I just focus on what I need to do,” he said, according to Reuters. “I just see it as high stakes race. Two athletes competing. We are two athletes at the top of our games who have to compete. That's how I see it.”

On the track, Gatlin has been the form man in 2015, with Bolt’s season disrupted by injury and subpar performances. But the Jamaican has so far always come good on the big occasion, with his only failure to win gold in both the 100m or 200m at an Olympics or World Championships since 2008 coming when he was disqualified for a false start in the 2007 World Championships 100m final.

Still, it was Gatlin who outlined his credentials in the opening round in Beijing, as he eased to a time of 9.83. Bolt, meanwhile, going in a later heat, had his usual slow start before jogging over the line in 9.96. Compatriot Asafa Powell went slightly faster than Bolt, as did young American Trayvon Bromell and Frenchman Jimmy Vicaut.  But the final on Sunday night at the Bird’s Nest is expected to be a straight fight between the two pre-championships headline-makers.

First, though, they will have to prevent any slip-ups in the semifinals, for which they have been separated, earlier in the evening.

Men’s 100m Schedule (all times EDT)

Semifinals: 7:10 a.m.

Final: 9:15 a.m.

TV and live stream info: In the United States, coverage will be tape-delayed on NBC from 1 p.m. EDT, with an online coverage available on NBC Sports Live Extra. Those in the United Kingdom can watch live on BBC Two from 11 a.m. BST, with a live stream available on the BBC Sport’s website.