French third seed Jo-Wilfried Tsonga suffered a shock 7-6 4-6 6-4 defeat by Dutch wildcard Igor Sijsling in the first round of the World Indoor Tournament on Monday.
The 27-year-old Tsonga squandered five breakpoints before surrendering the first set 7-3 in the tiebreak but appeared to have gained control of the match when he levelled the contest at one-set all.
But Tsonga's serve, which had produced 14 aces, collapsed in the 10th game of decisive set and that allowed his 77th-ranked opponent to pull off an unlikely victory.
"I can't say I played bad tennis but on this kind of surface matches are always tight," Tsonga, the highest seed in action on Monday in a tournament headed by Roger Federer, told reporters.
"It is disappointing to drop out early at such a big tournament."
Tsonga's compatriot Gilles Simon eased past German Daniel Brands with a 7-6 6-4.
Both players dropped their serve twice before Simon clinched the tiebreak and won the second to set up a second round match with Italian qualifier Matteo Viola.