Los Angeles - Controversial US sprinter Justin Gatlin, British long-distance world champ Mo Farah and two-time Olympic 100 metre champ Shelly-Ann Fraser-Pryce are some of the top talent competing at the Prefontaine Classic this weekend.
The IAAF Diamond League series hits US soil as a host of international stars will step up preparations for this summer's Rio Olympics by competing at Hayward Field, the US cathedral of distance running made famous by Steve Prefontaine.
The event was also hit by a number of late withdrawals as Olympic silver medallist Galen Rupp, Ethiopian distance runner Genzebe Dibaba and US sprinter Allyson Felix will not take part.
It was expected Dibaba would make an attempt at the 5 000 metre world record late Friday, but she pulled out with a toe injury suffered in training.
Felix is skipping the event due to a lingering ankle injury. She has already said that she hopes to double in the 200m and 400m in Rio de Janeiro.
Felix's absence means there won't be one final Hayward Field clash between Felix and Sanya Richards-Ross, who retired after the last Olympics.
Gatlin headlines an impressive list of talent in the men's 100 metre sprint that also includes Jamaican speedster Asafa Powell, Canadian Andre De Gasse, and defending 100m champ Tyson Gay of the United States.
Gatlin, who remains unapologetic after serving two doping bans, will have the Hayward crowd on his side Saturday unlike Diamond races in places like Europe, where the drug cheat label still hangs over his head.
Gatlin has never admitted to doping, saying that a 2006 failed test came as a result of a massage therapist rubbing testosterone cream on his legs. He also tested positive in 2001 for an amphetamine. He served a four-year ban, returning to the scene in 2010.
Gatlin posted a 9.94 second 100m victory earlier this year in China and is the heavy favourite heading into Saturday's race.
Britain's Farah, 33, is considered the world's leading long-distance runner and has not lost a 5 000 race since finishing second at the 2012 Prefontaine meet. He swept the 5 000 and 10 000 races at the 2012 London Olympics.
Fraser-Pryce is returning to competition at the Prefontaine after missing three meets with a foot injury.
It will be Fraser-Pryce's first competition after the toe injury made her pull out of a May 7 race in Jamaica and Diamond League meetings earlier this month in Shanghai and Rabat.