LAUSANNE, Switzerland (AP) The best 100-meter lineup so far in this world championship season sees six of the eight fastest men in 2015 race each other on Thursday.
Justin Gatlin of the United States, who has a world-leading 9.74 seconds, defends his two-season winning streak over 100 at the Athletissima Diamond League meet.
''This is the biggest race I'm going to be in for the season,'' Asafa Powell said Wednesday, days after the Jamaican former world record holder won at Paris in a season-best 9.81, second only to Gatlin's time.
The Lausanne lineup is missing Usain Bolt, though the Jamaican superstar has struggled in an injury-hit season and opted for the 200 before withdrawing.
Tyson Gay is here after winning the U.S. national title in 9.87, boosting a race that offers a key guide to dethroning Bolt at the Aug. 22-30 worlds in Beijing.
Still, the two-time Olympic champion's absence Thursday means the three highest-profile names in the marquee race have all served bans for testing positive for banned drugs
''People have to see it stay clean for many years to really forget about what has happened in the past,'' acknowledged Powell, whose case was resolved a year ago with a six-month ban for using a contaminated supplement.
Gay returned to the track last year after a reduced one-year ban for using a steroid precursor recommended by a coach. He called for greater understanding on Wednesday.
''When you put the (headline) doping or steroids and it's not clarified exactly what the situation was, I think it makes it hard for people to believe in the sport,'' said Gay, the 2007 world champion. ''Some time we have to get a fair shot as well. To show the kids that you can make a mistake and come back.''
Gay also suggested ''bumps in the road'' for his generation were less serious than previous tainted sprinting eras.
''Our situations were actually minor compared to a lot of things back in the past,'' the 32-year-old American said. ''None of us were involved in situations with syringes and real steroids and undetectable things like that.''
At age 33, Gatlin is back on top 11 years after his Athens Olympic title and having completed a four-year ban in 2010 for excessive testosterone.
Gatlin won his 18th straight 100 race on Tuesday in Budapest, Hungary - a streak that helped win him the Diamond League title last season and direct entry to the worlds.
''All power to him,'' Gay said of his American teammate. ''That's tough to be a sprinter and have a good day every race.''
Before that praise, Powell noted he and Gay are above Gatlin on the all-time list led by Bolt's 9.58 at the 2009 worlds.
''He is like the fifth fastest man in the world,'' Powell chided reporters about Gatlin. ''I don't know why you think he can't be beaten.''
Double Olympic champion Mo Farah is another main attraction at Athletissima, competing for the first time since British broadcaster the BBC last month linked his American coaching base to doping.
Farah, who runs in the 5,000, has defended coach Alberto Salazar who denies any wrongdoing.
The 200 is the main women's sprint at Athletissima, and has added significance for Olympic champion Allyson Felix.
Felix could run in the 200 or 400 at Beijing - where the schedule makes doubling up too difficult - and her race Thursday could be decisive for the American and her coach Bobby Kersee.
''Bobby is the one who ultimately will make the decision,'' Felix said. ''After I run here he will make the final suggestion.''