(Reuters) - American Justin Gatlin stepped up his preparations for the Rio Olympics with an impressive victory in the 100 meters at the Diamond League in Shanghai on Saturday.
Gatlin, who has twice served bans for doping, was unbeaten at 100 and 200 meters in 2015 until he faced an out-of-form Usain Bolt in the world championships in Beijing last August.
Bolt, the Olympic champion, won both the races but Gatlin showed in Shanghai that he was gearing up to challenge the Jamaican again at the Rio Games in August.
Gatlin led from the start and won in 9.94 seconds with Qatar's Femi Ogunode, the quickest over 100m this year with 9.91 in Florida last month, finishing second in 10.07.
"I came out here to execute and I know being an Olympic year, it is a long season and my coach and I have a plan," Gatlin said.
"He is training me like Mike Tyson to knock out the opposition and keep swinging.
"The ankle injury over the winter made it a difficult preparation, but Diamond League races are important to win."
Olympic and world men's 800m champion David Rudisha had a disappointing outing as he fell behind in the home stretch and finished fifth with Ferguson Cheruiyot Rotich snatching an unlikely win in 1:45.68.
The Kenyan world-record holder's time of 1:46.24 was his slowest for five years.
"I'm so upset. I lost two seconds because of the start. There where high jumpers in the lane and they start (the race)," an visibly upset Rudisha said.
American Aries Merritt, the Olympic 110m hurdles champion, was disqualified for a false start as Omar McLeod produced the year's first sub-13 second performance to take his second Diamond League win this season.
Unfazed by two false starts, world indoor champion McLeod made a strong start and went across the line in 12.98 seconds.
In the pole vault, American Sam Kendricks set a personal best to beat world record holder and Olympic champion Renaud Lavillenie and world champion Shawn Barber in a major upset.
Kendricks underlined his potential for Rio by bettering his previous best by six centimeters by clearing 5.88 at the third attempt. Lavillenie managed 5.83, failing twice at 5.88 before making one effort at 5.93. Canadian Barber was third with 5.70.
"I just had to take the competition one height at a time and I am pleased to come out on top," said Kendricks. "I have finished second, third, fourth and fifth in Diamond League meets before, never first."
Writing by Sudipto Ganguly in Mumbai; Editing by Ken Ferris