French seventh seed Jo-Wilfried Tsonga was upset 7-6 6-2 by Australian qualifier Chris Guccione in the second round of the Cincinnati Masters on Wednesday.
Tsonga, who beat Roger Federer in Montreal last week, lost the first-set tiebreak 14-12 after the big-serving Guccione saved three set points.
The world 124 then cruised through the second set and clinched victory with his 20th ace.
Guccione now plays either Czech Tomas Berdych or Philipp Petzschner of Germany.
Fourth seed Novak Djokovic found the going easier and moved into the third round with a 7-6 6-4 victory over Croatian Ivan Ljubicic.
The Serb, runner-up last year, edged the first set and then broke once at the beginning of the second to secure a meeting with either American John Isner or Jeremy Chardy of France.
The match was played in overcast conditions and with the temperature expected to rise significantly later in the day, Djokovic said he had been fortunate.
“I think I was a bit lucky today to play first,” he told reporters. “It can get very hot here so it’s best to either play first or late at night.”