Sanchez left out to dry by Gordon
Trinidad and Tobago's Jehue Gordon (L) and US Michael Tinsley (R) stretch for the line in the 400 metres hurdles final at the 2013 IAAF World Championships at the Luzhniki stadium in Moscow on August 15, 2013.
Gordon, sixth in the London Olympics and fourth in the 2009 worlds in Berlin, came from nowhere to snatch gold in 47.69sec, with American Olympic silver medallist Michael Tinsley taking silver at just one-hundredth of a second.
The battle for the third spot on the podium was tight, but went the way of Serbia's Emir Bekric, the European silver medallist, for a first-ever world medal for his country.
Cuban Omar Cisneros beat Sanchez for fourth spot for a sorry end to the world champs for the Dominican Republic star, who turns 36 at the end of August.
The London Olympic champion had picked the little-known Gordon as favourite for the race and proved to be right on the money.
"I started well after feeling good in warm-up," said Sanchez. "But after the third hurdle I made some mistakes and lost too much time.
"I came back to finish strong but it was not enough to come back after those mistakes - they definitely cost me a medal."
Sanchez was non-committal about his likely participation in the next world championships in Beijing in 2015.
"I don't know," he said. "I need to think about it. There's still two long years ahead."
The 21-year-old Gordon quickly fixed his long-term goal as becoming Olympic and Pan-American champion.
"Those victories won't come easy, I know, but I'll just keep working and believing in myself," Gordon said.
"After I crossed the line my heart stopped for a minute, I just wanted to look up at the screen and see my name there."
Tinsley was left ruing his final run-in to the line, when he thought he had the better of the Trinidadian, for whose country it was only the second world gold after Ato Boldon's 200m victory in 1997.
"Jehue and me both came down on the 10th hurdle and I thought I could get him, but he came back at me on the line," said Tinsley.
"I would lie if I said I didn't want that gold medal. It was really close, a tough race."
Puerto Rico's Olympic bronze-medal winner Javier Culsom finished sixth, ahead of Senegal's Mamdou Kasse Hannne with American Kerron Clement, world champion in 2007 and 2009, finishing eighth and last.