But as the gun went, the 25-year-old shot out of the blocks matching Liu’s famed blitz start and was never headed as he created one of the shocks in Istanbul.

So it is hardly a surprise that Liu regards Merritt as his main rival come Shanghai on Saturday evening.

In Istanbul, by way of explaining for his shock defeat, Liu said: “I knew Aries Merritt is a fast starter so I got out in a rush and was not able to control my technique.”

With the benefit of that experience behind him, it will be interesting to see how Liu deals with the American on Saturday.

Merritt has been showing promise for some time, but finally broke into the big-time with his first major title in Istanbul. It was also the first time in five tries that he managed to defeat the Chinese 2004 Olympic champion so it was some achievement.

But the writing had been on the wall for Merritt since he lifted his national indoor crown in Albuquerque in February in a personal best 7.43.

In his wake on that occasion was double Olympic silver, Terence Trammell, who was third, and David Oliver in fifth, both formidable rivals.

Still, indoor is one thing and outdoor is an entirely different challenge. The extra 40 metres can make a big difference. But this year Merritt has made the transition without batting an eyelid.

His previous personal best for the longer distance harked back to 2007 in Stockholm when he clocked 13.09, but in Fayettville at the beginning of this month Merritt demolished that with a quality 13.03.

That came after an even faster heat of 12.99 that was unacceptable for record purposes owing to a following wind of 2.9mps. Merritt has been aiming for a sub-13sec clocking for some time and though on this occasion the wind was a little too strong, they always say the importance of a fast time is as a boost to confidence no matter how much it is wind-aided.

His new legal lifetime best puts Merritt at the top of the world lists at this stage of the season. But Liu is within striking distance because two days after Merritt set new career best figures Liu responded with a 13.09 in Kawasaki. So the stage is set for a showdown between the top two in the world so far this season.

This year is one of enormous importance for Merritt because it represents a golden opportunity to qualify for his first Olympics. In 2008 he could only finish fourth in the sudden-death American trials and did not make the team.

Prior to those trials, Merritt had suffered from a hamstring injury and finished agonisingly off the podium. Then in the 2009 world championships he twisted an ankle in warm-up and did not get past the first round.

A stress fracture put paid to 2010 and last year in the Daegu disaster-prone final he hit a hurdle and finished fifth.

But this year has seen a fresh approach. In common with most top hurdlers including Liu, Merritt has shortened his approach to the first hurdle to seven steps instead of eight.

“When you do eight steps, some hurdlers have to kind of slam on the brakes in order to take the hurdle,” explained Merritt. “With seven steps you can really drive through a hurdle and take it with a little more aggression.

Shanghai will be the sixth meeting between Merritt and Liu. Will the new-style American make it two wins in a row over the former world record holder?  Shortly after 21:54 local time Shanghai on Saturday we will have the answer.