World number one Novak Djokovic needed three sets to get past Gilles Simon in the Western and Southern Open second round but Jo-Wilfried Tsonga lost to Mikhail Youzhny in his opener two days after winning the Rogers Cup in Toronto.
Djokovic grabbed the crucial third set break in the seventh game to prevail 6-3, 4-6, 6-4. Coming off a round-of-16 loss in Toronto, the Wimbledon champion pulled out the crucial points when he had to.
Earlier, Tsonga was brought back down to earth with a bump with a 6-1, 6-4 loss in his tournament opener to Russian Youzhny.
The 12th-seeded Frenchman, whose victory over Roger Federer in the Toronto final was his fourth straight win over a top -10 opponent, including a win over Djokovic, offered little resistance as Youzhny advanced in 68 minutes.
"I just gave everything last week," said Tsonga, who was unable to get any practice in on Monday due to rain. "Before the match I believed I was able to play at the good level but on the court I realized that it's going to be impossible and it was."
Third-seed Stan Wawrinka of Switzerland pushed through his evening second round contest with German qualifier Benjamin Becker 6-3, 7-6.
Croatian 14th-seed Marin Cilic breezed to a 6-3, 6-4 first round win over Spaniard Feliciano Lopez, who lost to Federer in the Toronto semis.