The Wimbledon champion was joined at the exit by another grand slam winner, Australian Open champion and third seed Stan Wawrinka, who was beaten 7-6 (8) 7-5 by South African Kevin Anderson.
French 12th seed Richard Gasquet was also a third round casualty, pulling out of the tournament with abdominal pain and handing twice Canadian champion Andy Murray direct passage into the quarter-finals.
A three-time winner on the Canadian hard courts, Djokovic never found his rhythm in Toronto needing a third set tiebreak to get past Frenchman Gael Monfils on Wednesday in his opening match.
Playing his first event as a married man, the Serb had reached the semi-finals or better in all seven tournaments he had played since a quarter-final loss at the Australian Open, winning titles at Indian Wells, Miami, Rome and Wimbledon where he reclaimed the top ranking.
“I haven’t played even close to what I intended before going to the court,” said Djokovic. “No baseline, no serve, no return.
“Just generally very bad day, very poor performance. Couldn’t do much.”
While Djokovic will move onto Cincinnati to prepare for next week’s event and continue his buildup to the U.S. Open, Tsonga moves into the final eight and meeting with Murray.
The Frenchman has found success over the years on the Canadian hard courts reaching the semifinals in two of his previous three visits and with a quarterfinal win over Murray can return to the final four again.
Tsonga’s win over Djokovic marked the third time he has beaten a world number one but was also the first time in their last 12 meetings that the 13th seeded Frenchman had gotten the better of the Serb.
“We grew up together on the tour, we had many good years,” said Tsonga, who is now 6-14 lifetime against Djokovic. “When you play against him you know it’s going to be difficult.
“Even if the score today seemed easy, it’s never easy against him.
Anderson, meanwhile, is proving to be a bit of boogeyman for Wawrinka, the South African having ended the Swiss’s 13-match win streak with a fourth round upset earlier this season at Indian Wells.
The South African will next meet Bulgarian seventh seed Grigor Dimitrov, who was forced to sit out last week’s event in Washington with the flu but looked back to full health taming Spain’s Tommy Rebredo in three sets 7-5 5-7 6-4.
“It’s tough to lose that one,” admitted Wawrinka. “It was an okay tournament, nothing special. But I play four matches, singles, doubles together, and did a good week of preparation.
“In general, I’m feeling great. I’m feeling physically good. I’m moving well. I’m playing well. It’s just that I need more matches to be really at the top.”
Fifth seed David Ferrer also moved on with at 1-6 6-3 6-3 win over Croatia’s Ivan Dodig and awaits the winner between second seed Roger Federer and big-hitting Marian Cilic who meet later on Thursday. (Reuters)