Pablo Carreno-Busta's push for an ATP Finals spot suffered a blow when he was beaten by Diego Schwartzman in the Vienna Open, while Dominic Thiem suffered a second-round exit on home soil.
Carreno-Busta occupies the final qualifying spot place for the lucrative season-ending tournament at the O2 Arena next month, but the Spaniard is in danger of missing out after a 5-7, 6-1, 6-1 loss to the unseeded Schwartzman on Thursday.
Juan Martin del Potro can move above Carreno-Busta if he wins the Swiss Indoors Basel this week following Schwartzman's second-round victory, which gave him some measure of revenge for a defeat in the US Open quarterfinals.
Carreno-Busta recovered from losing the first three games to win the opening set, but was broken three times in the second and twice in the decider to bow out.
Richard Gasquet accounted for Thiem, coming from a set down to beat the second seed 4-6, 7-5, 6-1.
World No. 6 Thiem has endured a poor late-season run and Gasquet dealt him another setback, breaking three times to reach the last eight.
Jo-Wilfried Tsonga, last year's runner-up, has won 18 of his 20 indoor matches this season and remains in the hunt to return to London following a 6-7 (5-7), 7-6 (9-7), 6-1 victory over qualifier Damir Dzumhur.
The powerful Frenchman saved a match point in the second-set tie-break and went on to book a quarterfinal against top seed Alexander Zverev.
Kyle Edmund, Lucas Pouille and Jan-Lennard Struff also reached the last eight on Thursday.