Big, strong and determined, American David Oliver dominated the world's high hurdles during a perfect 2010 outdoor season but the path has not been as clear in 2011.

Chinese former world record holder Liu Xiang, employing a new starting technique, ended Oliver's 18-meeting win streak earlier this month in Shanghai. The performance was Liu's finest since a 2008 injury ended the 2004 Olympic champion's dream of a golden repeat in Beijing.

The friendly rivals will clash again on Saturday in Eugene, Oregon, in one of the highlights of the Prefontaine Classic Diamond League meeting.

Cuba's Dayron Robles holds the world record for 110 meters hurdles at 12.87 seconds but Oliver said he believed Liu was the best. "He is the greatest hurdler of my generation in my opinion," the American record holder said.

"He set the world junior record, tied and then broke the world record, became the first to run under 12.90 seconds, then was injured and has come back at almost as good a level as when he left," Oliver said.

"He has got such great technique."

Oliver has rediscovered that frequently in a rivalry stretching back to 2005. Seven times in their eight joint finals Liu has prevailed. "Guys like he and Robles. They are two people who are like one of a kind," said the 29-year-old Oliver. "They can accomplish in one or two races what it takes a guy like myself four or five races.

"I have to walk my times down, but Liu can open (the season) in 13.0."

A poor start eroded Oliver's chances of defeating Liu in Shanghai, but the American's goal remains the same, to win his first world championship title in August with a healthy Liu and Robles in the race.

"Just because something happens at a meet, we are not going to hit the panic button and change the whole game plan," Oliver said. "Last season I was coming off that major (calf) injury of '09 so I had to prove not only to the track world but myself that I still have it. So we prepared for every race like it was a championship event."

This year, the buildup has been slower with Oliver still heavily into weightlifting and running 300 meters trials in practices, much longer than usual for late May.

"The plan is to be fresh later," he explained.

He will not compete between the Prefontaine Classic and the late June US championships/world trials and there are only a limited number of possible races before the world championships start on August 27 in Daegu, South Korea.