Vancouver's Vasek Pospisil has advanced to the second round of the Western & Southern Open near Cincinnati.

He defeated Radek Stepanek of the Czech Republic 5-7, 6-1, 7-6 (4) on Tuesday and next will play No. 2 Roger Federer.

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."

Tsonga, Venus Williams ousted

Meanwhile, Jo-Wilfried Tsonga and Venus Williams left their winning touch back in Canada.

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.

Williams knocked off sister Serena while reaching the finals in Montreal on Sunday, finishing runner-up. She lost to Lucie Safarova 6-7 (2), 6-3, 6-4 in the first round Tuesday.

"I wish I could have felt today like I did in Montreal, just to make it more competitive," Williams said.

Williams and Tsonga had energizing weeks in Canada and hoped to keep their momentum going in Cincinnati, using it as a springboard to the U.S. Open. Both soon realized their successful weeks came with a cost.

'Quick turnaround'

Williams arrived Sunday night and opened Tuesday morning, leaving little time to recover from her deep tournament run.

"Yeah, it was definitely a quick turnaround," she said. "Maybe it would have been a little better to play a little later in the day. But I think she just played so well. No matter what shot I hit, she hit a winner."

Safarova led 5-2 in the third set and appeared to have won a match point, but Williams challenged and the call was overturned. Williams rallied to win the set and then another.

The tournament lost its other defending champion when Victoria Azarenka withdrew on Tuesday because of an injured right knee. Defending champion Rafael Nadal withdrew before the tournament because of an injured wrist.

In other men's play, Marin Cilic advanced to the second round with a 6-3, 6-4 win over Feliciano Lopez, while qualifier James Ward, ranked 148th, upset No. 32 Guillermo Garcia-Lopez, 6-2, 3-6, 6-1.

The biggest intrigue is whether Novak Djokovic can finally win the one tournament that has eluded him. He has finished runner-up in Cincinnati four times. If he wins this week, he'll become the first with titles at all nine ATP Masters events.

Djokovic was to play his opening match Tuesday night.

On the women's side, Suarez Navarro also needed three sets to get past Tsvetana Pironkova 6-3, 1-6, 6-2.

With files from The Associated Press