Tyson Gay sent a warning to his rivals that he still has plenty left in the tank after running the fastest 100 metres this year.
The American stopped the clock at 9.79 seconds in his first outing this year during a low-key meet in Florida but said he expected to go a lot faster once he was fully fit and training at maximum speed.
"It was my first race. I basically just wanted to see where I was at and how my body felt after the race," he told a news conference on Thursday.
"I was about 75 per cent. I've even been training at 75 percent instead of smashing on the gas."
Gay had earlier announced that he was not planning to race the 200m this season because he wasn't completely fit after battling a painful hip for the past three months and wanted to focus his attention on the 100m.
His main goal is this year's world championships in South Korea, where he will likely face world record holder Usain Bolt, but he will face an early test of his speed this weekend, when he lines up against his Jamaican training partner Steve Mullings in the Diamond League meet at New York.
Mullings won the 100m sprint at last week's Diamond League event in Oregon with a time of 9.80.
"He was running 10.00, now he's running 9.80, I have to step my game up to another level and see what happens," Gay said.
Gay, whose personal best time of 9.69 is second only to Bolt's world record of 9.58, said his battle with injuries may ultimately prove a blessing in disguise.
"It's very frustrating but at the same time, in some ways running with injuries or running hurt has made me the person I am today, made me fight harder," he said.
Saturday's meeting at Randall's Island near Manhattan also features two-time women's world high jump champion Blanka Vlasic of Croatia and three-time 200m world champion Allyson Felix of the United States.
Vlasic, the 2010 World Athlete of the Year, is ramping up after an illness in January led her to skip the indoor season.
Her personal best of 2.08m is just one centimetre below the world record set by Stefka Kostadinova of Bulgaria at the 1987 world championships in Rome.
"I can't not think about (the world record), because somebody always asks me about it," Vlasic said. "I'm trying not to be under too much stress. It's something that I would like to do.
"I'd like to go one step forward to break my PB (personal best), and my new PB would be also the world record."
The meeting also presents South Africa's Oscar Pistorius with another chance to qualify for the 400m at the world championships and London Olympics.
A double amputee who has fought a long legal battle to compete against able-bodied athletes, he has a best time of 45.61 and needs to get down to 45.25.
"Every race, we pretend is the race I need to qualify," said Pistorius.