Stanislas Wawrinka ran into a spot of bother but stayed on track for the ATP World Tour finals by seeing off Spain's Feliciano Lopez 6-3 3-6 6-3 in the second round of the Paris Masters on Wednesday.
The seventh-seeded Swiss, looking to qualify for the season-ending event for the first time, started the week in eighth place in the ATP Race to London.
Three tickets remain up for grabs, with Rafael Nadal, Novak Djokovic, David Ferrer, Juan Martin del Potro and Tomas Berdych having already qualified.
World number four Andy Murray of Britain has pulled out because of back surgery.
Wawrinka's victory means that Spaniard Nicolas Almagro is ruled out of the race.
The Swiss served 19 aces and prevailed in under two hours at Bercy, recovering quickly after a dip in concentration cost the 28-year-old the loss of the second set.
His compatriot Roger Federer will qualify for next week's finals at the O2 Arena in London if the 17-times grand slam champion beats South African Kevin Anderson in the second round.
World number one Nadal starts his Paris campaign with a second-round match against fellow Spaniard Marcel Granollers later on Wednesday.
Paris Masters Results:
Juan Martin Del Potro (Argentina) beat Marin Cilic (Croatia) 6-4 7-6(3)
Stanislas Wawrinka (Switzerland) beat Feliciano Lopez (Spain) 6-3 3-6 6-3
Gilles Simon (France) beat Nicolas Mahut (France) 6-4 6-7(5) 7-6(3)
Nicolas Almagro (Spain) beat Ivan Dodig (Croatia) 6-4 6-3
John Isner (U.S.) beat Michal Przysiezny (Poland) 7-6(3) 4-6 6-3
David Ferrer (Spain) beat Lukas Rosol (Czech Republic) 6-0 2-6 6-3