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Tyson Gay, 28, will miss out on a 100m clash with Usain Bolt at this year's World Championships, holding in South Korea, after pulling out of the US National trials with a hip injury.
Gay, who has run the fastest 100m in the world this year of 9.79 seconds, had been expected to be one of the main challengers to Jamaican world record-holder Bolt in the 100m in South Korea.
Gay's US record of 9.69sec makes him the second-fastest man in history behind Bolt, who holds the world record of 9.58sec, and he beat the injury-affected Olympic champion in Stockholm last year.