Trinidad and Tobago's Renny Quow is relying on mental toughness to tackle other world-class rivals in Friday's men's 400-metre final at the 12th IAAF World Championships at the Berlin Olympic Stadium.

The 21-year-old Quow, also a finalist at the Olympics in Beijing last year, used a blistering finish to snatch second place in a personal-best time of 44.53 in the second semi-final heat on Wednesday.

A gold medallist at the 2006 IAAF World Junior Championships, Quow has been prominent without being dominant in his fledgling senior career and he is ready to take on a positive frame of mind entering the race for gold.

Mentally strong

"This is a different level, you know. To make it here, you don't just have to be (physically) strong but you have to mentally strong," he said.

Entering the home stretch off the pace in his semi-final run on Wednesday, Quow rallied with a terrific burst over the last 80 metres to follow Olympic champion LaShawn Merritt home.

Merritt, of the United States, clocked a world-leading 44.37 seconds to beat Quow with Cuban William Collazo third in a personal-best 44.93.

Quow, drawn in lane four, said he measured his race against Merritt, who was very strong early. He says he was not flustered when the American - in lane three - went past him down the backstretch.

"I knew he would have passed me - he got out really strong, I had expected that, so I kind of anticipated him and tried to make back up on the last hundred," Quow said.

Quow also knows he must recover quickly to deliver another top effort in today's final.

"I'll try but right now I am just going to go back home and relax, so we will see," Quow said.