Liu Xiang's hurdles rematch with Jason Richardson is the most anticipated race of the Shanghai Diamond League meet on Saturday.
Dayron Robles won the 110-meter hurdles at the world championships in Daegu, South Korea, last August, but was disqualified after Liu appealed. Robles smacked Liu's hands over the last hurdles. Richardson was promoted to the gold medal, and Liu received the silver.
Liu, the 2004 Olympic gold medalist and last year's champion in Shanghai, is coming off a victory in his first outdoor race of the season in Japan two weeks ago.
The hurdles field also includes Americans David Oliver, the 2008 Olympic bronze medalist; Terrence Trammell, a two-time Olympic silver medalist; and Aries Merritt, who defeated Liu in March to win the world indoor 60-meter hurdles.
Robles, the 2008 Olympic champion, wasn't entered.
Liu joked that the incident in Daegu made his friendly relationship with Robles "even better." He added that a healthy rivalry was important to the sport and it motivated him to continue improving his form.
"Of course, rivals do affect athletes mentally, but if you are competing with top-notch athletes, you will push each other, you will encourage each other," he said.
"Tomorrow's competition will be very fierce. What I want is to fulfill my performances during training so that I can be satisfied with myself."
Richardson said he's eager to face Liu again to show he can be considered a serious contender in London.
"I definitely don't have any pressure because Liu is definitely at home and there are other rivals in here who have run faster, but what I do enjoy is running against the odds," he said.
In another top matchup, Jamaica's Veronica Campbell-Brown will face American Carmelita Jeter in the women's 200. Last year's race saw Campbell-Brown win by 0.03 seconds.
Campbell-Brown, a two-time Olympic gold medalist in the 200, said she's using the race to gauge what she needs to work on with less than three months to go until the Olympics. American Allyson Felix beat Campbell-Brown in the 100 last week at the season-opening Diamond League event in Doha, but isn't competing in Shanghai.
Another Jamaican sprinter looking to build up his confidence was Asafa Powell, the former 100 world record-holder. Powell has been eclipsed by teammates Usain Bolt and Yohan Blake, but he finished second to Justin Gatlin in Doha in 9.88 seconds.
Bolt, Blake and Gatlin aren't in Shanghai, so Powell's toughest competition should come from Kim Collins of St. Kitts and Nevis, a former 100 world champion, and Jamaicans Michael Frater and Nesta Carter.