VALENCIA (AFP) - Second seed Jo-Wilfried Tsonga, ranked number eight in the world was beaten 7-6, (7/5), 6-2 in the second-round of the Valencia Open on Thursday by world number 116 Sam Querrey of the United States. The defeat is a severe blow to Tsonga's chances of taking one of the three remaining berths open for qualification to the ATP World Tour Finals in London later this month. Tsonga was the number two seed in Valencia and the shock win for Querrey means he will now face Argentine Juan Martin Del Potro in Friday's quarter-final. Del Potro won the final second-round game here on Thursday evening beating South Africa's Kevin Anderson 6-4, 6-4, and while currently ranked 11th in the world, further success in Valencia could mean he advances towards a place in London at the expense of Tsonga and world number nine Nicolas Almagro who was a first round loser here. Joint-owner of the Valencia Open Juan Carlos Ferrero made sure of his place in Friday's quarter-finals by beating Alex Bogomolov Jr. of the USA 7-6 (7/2), 4-6, 6-2 in almost three hours. Two very close first sets were shared before Ferrero made his experience show by racing into a 5-0 lead in the decisive third set. Bogomolov Jr, ranked at a career high 33, may have been suffering from his exertions on Wednesday when he beat Feliciano Lopez in three sets in the final game of the first round. He did rally slightly to pull two service games back but Ferrero made sure he reached the quarter-final stage in his home city for the first time ever.