American Kristi Castlin has stunned a very high-class field to win the 100m hurdles at the Drake Relays event in Iowa, USA.

The 25-year-old, a relatively unheralded athlete, stormed through from the outside lane to take the win in a meet record time of 12.58 seconds, reports ESPN.

In the process of claiming her most famous win, Castlin inflicted pre-race favourite Brianna Rollins' first defeat in 19 races. The world champion also ran 12.58 seconds but was pushed into second by five thousandths of a second.

It was a result that stunned everyone in the stadium, but Castlin was just excited by the performance. 

"I had a little chip on my shoulder," she said. "Sometimes it's tough to run out of lane eight because you don't know what's going on. I just had to execute my best race. That's why I was so excited, because I was out there by myself."

Rollins wasn't the only high-profile athlete defeated by Castlin, though. Defending champion Queen Harrison, Dawn Harper-Nelson and Britain's world championship bronze medallist Tiffany Porter were also in the field.

Porter finished fifth in the meet, as she steps up her preparation for the Commonwealth Games in Glasgow this July.

The 26-year-old only changed her allegiance from the USA to Great Britain at the end of the 2010 season, meaning this will be her first Commonwealth Games. With the absence of all of the Americans, it is expected to be a showdown between Porter and Sally Pearson - the Olympic champion.

Before that, though, comes the Diamond League. And if she repeats the kind of performance she has just produced, it's doubtful Castlin will remain unheralded for very long.

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