If you are in 10.10-10.20 shape you have a chance to win as a backmarker. (see Josh Ross). To win, Asafa would only need to be capable of running 120m on grass (very slightly uphill) in under 12s. The maximum headstart is 10m, but it seems to be mainly 10.50-10.70 sprinters running off a 5-7m mark that win.