Dawn Harper knows better than anyone never to underestimate Sally Pearson.
When the American won her Olympics 100m hurdles title five years ago in Beijing, it was the then 21-year-old Australian chasing her home for silver.
Four years later in London, Harper ran a big personal best of 12.37 seconds in the Olympic final, but it wasn't quite enough to reel in the Australian, who won by two hundredths of a second.
So even though Pearson has had to battle two hamstring injuries this year, Harper is still expecting big things from her at the world championships in Moscow.
Pearson did not begin racing this year until June, with her best victory coming at the Diamond League meet in London in 12.65 - well shy of the PB of 12.28 she set when winning gold in the 2011 world championships final.
Young American star Brianna Rollins tops the 2013 world list with 12.26, while Harper has run 12.53.
"I knew that it would be really tough (for Pearson) because she was telling me she thought she needed races and I knew she had races lined up," said Harper.
"I was like, 'this is going to be tough' but if you have run the times she has, you have to have a sense of 'me and my coach can figure it out; we can figure it out'.
"She still has time to train.
"When you are in that situation, you are thinking that you still have up until the day before to still click."
But the scenario is clearly different to last year, when Pearson arrived in London as the red-hot Olympic favourite, having dominated the European summer season.
"There is a difference but also no, because she's such a great competitor," said Harper.
"I see her as being very similar to myself in that no matter how it's gone before, this is a whole new ball game."
The other big challenge is likely to come from Rollins, whose flying time of 12.26 at the US trials in June lifted her above Pearson to equal third on the all-time list.
"I was definitely in the zone but it felt really smooth and relaxed honestly and I guess that is why I put the race together," said Rollins.
"Being consistent boosts your confidence up.
" ... I have been pretty surprised (with my breakout year) but my coach always told me that I had it in me and I just had to put the hard work in for it to come out."
Harper admits she was surprised with Rollins' time.
"Typically people go their whole lives and don't even imagine a 12.2," said Harper.
"For me, it says that she and her coach have put together some things.
"But when you get here, you have to do it again.
"You have to do it with the big dogs - you've got to do it with the stands full."
The first round of the 100m hurdles is on Friday, with Frenchwoman Cindy Billaud the next best-credentialled athlete in Pearson's heat.
