Rising US hurdling star Brianna Rollins has hurt her knee in training less than a week ahead of a much-anticipated showdown with Sally Pearson.
Rollins, 22, burst onto the scene with a blistering time of 12.26 seconds at the US national trials in June, 0.02sec faster than the Australian Olympic and world champion has ever run.
But Rollins has deliberately avoided taking on Pearson in the intervening two months, choosing to only race twice in Europe.
At the same time, Pearson was building her form and fitness in a solid six-meet program after recovering from two hamstring injuries.
The Australian took confidence from her most recent race, a victory in 12.65 at last month's Diamond League meet in London.
Rollins' training mishap will add further to the intrigue.
"They need to invest in some plastic hurdles. This isn't the 1970s," Rollins tweeted on Monday.
"Banged my knee in training two days ago and still feel the pain."
Rollins heads a strong four-pronged American 100m hurdles squad which also includes 2008 Olympic champion Dawn Harper-Nelson, Queen Harrison and Nia Ali.
But Australian head coach Eric Hollingsworth insists that Pearson still deserves to start as favourite to successfully defend her world title in Moscow.
The 100m hurdles heats are on Friday, with the semi-finals and final scheduled for Saturday (early Sunday morning AEST).
