Gilles Simon's bid for a berth at the World Tour Finals suffered a setback when the French fifth seed was beaten 6-4 4-6 6-3 by Russian former world number three Nikolay Davydenko in the first round of the Valencia Open on Monday.
Davydenko, who has slipped to 36th in the rankings and is unseeded for the Spanish hard-court event, had lost five in a row against the world number 12 but broke Simon four times and lost his own service only twice to set up victory.
The 30-year-old will play the winner of Monday's match between French qualifier Nicolas Mahut and unseeded Spaniard Guillermo Garcia-Lopez.
Simon has only the Paris Masters left to try to secure a spot at the season-ending finals in London starting on Nov. 20.
Top seed and defending champion David Ferrer of Spain takes on unseeded compatriot Fernando Verdasco in the pick of Tuesday's first-round action.
World number five Ferrer has already qualified for the eight-man London finals along with Novak Djokovic, Rafa Nadal, Andy Murray and Roger Federer.
Czech Tomas Berdych, Jo-Wilfried Tsonga, who is playing in Valencia, and American Mardy Fish currently occupy the next three spots in the race to secure a place in the season finale.