MASON, Ohio -- Vancouver's Vasek Pospisil was the sole Canadian in action at the Western & Southern Open in Cincinnati although he played twice. Pospisil defeated Radek Stepanek of the Czech Republic 5-7, 6-1, 7-6(4) in the men's singles tournament.
Pospisil and American partner Jack Sock also won, dispatching the team of India's Rohan Bopanna and Pakistan's Aisam-Ul-Haq Qureshi 7-5, 6-2.
Top-ranked Novak Djokovic came back to beat Gilles Simon 6-3, 4-6, 6-4 in his opening match.
The Cincinnati tournament is the only Masters series event Djokovic has never won, finishing as the runner-up four times. If he wins this week, he'll become the first with titles at all nine ATP Masters events.
First, he had to get past Simon. He had trouble putting away the Frenchman, whom he has now beaten eight straight times. The opening game of the third set went 20 points and 15 minutes, with Simon surviving six break points.
Djokovic finally broke through for a 4-3 lead and served out the 2-hour, 9-minute match. The last set alone took 59 minutes. Djokovic had 36 unforced errors in the breezy evening conditions.
"Let's be honest: I don't enjoy playing bad," Djokovic said. "I don't enjoy missing a lot of balls from the baseline. That was frustrating for me.
"I'm not playing at a level that I need to be, and it's obvious. I keep pushing myself."
Jo-Wilfried Tsonga followed his week of big upsets with an early exit Tuesday, losing his opening match at the Western & Southern Open. Two days after he won his second Masters title by beating Roger Federer in Toronto, he fell to Mikhail Youzhny 6-1, 6-4.
"I don't have the energy to compete," Tsonga said after the 68-minute match. "I just gave everything last week. Before the match, I believed I was able to play at a good level. But on court, I realized that was going to be impossible. And it was."
Tsonga beat Djokovic, Andy Murray, Grigor Dimitrov and Federer to win in Toronto, the first time in 12 years a player beat four straight top 10 opponents at a Masters tournament. He arrived Monday and couldn't practice because of rain. He plans to rest for a few days.
"I didn't have enough today to compete at a good level," he said.
Freelance writer Mark Schmetzer contributed to this report.