World 100m record holder Asafa Powell could miss the Golden League meeting in Paris on 6 July after suffering a groin injury at the Jamaican championships.
Powell shared the $1m for winning the Golden League last season
If he is ruled out, he would also miss out on a possible $1m bonus.
Any athlete who wins all six of their events during the Golden League season is eligible for the £500,000 prize.
The 24-year-old Powell, who shared the $1m with Sanya Richards and Jeremy Wariner last season, won the opening Golden League 100m in Oslo in June.
Powell's manager, Paul Doyle, said he was "50-50" to compete in Paris, but added that the sprinter was not suffering from the same niggling groin injury that plagued him in 2005.
There have been reports that Powell was in some discomfort and could not feel his left leg when he tried to lift it up, but Doyle insisted: "He is walking around pain free."
Powell twice nearly came to halt during the 100m in Jamaica, but still won in a time of 10.04 seconds.
After finishing he lay on his back for about three minutes before being helped away for treatment.