MASON, Ohio (AP) -- Serena Williams pumped her fist after each important point and screamed as she smacked another emphatic shot. The defending Cincinnati champion wasn't going to ease into the tournament.

Williams put a lot of emotion into her opening match at the Western & Southern Open on Wednesday, a 7-5, 6-3 victory over Tsvetana Pironkova that made her the first of the top seeds to advance.

Novak Djokovic won his rain-delayed opening match, beating Benoit Paire 7-5, 6-2. Third-seeded Andy Murray and eight-seeded Rafael Nadal also advanced in rain-delayed matches that ended after midnight.

Williams won the Cincinnati tournament for the first time last year, getting one of the few titles that had eluded her. This year, she's using it as a final tuneup for the U.S. Open, where she'll be the focus as she tries to complete a rare Grand Slam sweep.

For her, this week is about getting her game ready to take a swing at history.

"I think it could be a lot better," she said. "It's not where I would want it ideally, but, you know, I'm going to have to fix that more mentally than anything. I think once I lock in there I will be OK."

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She's already starting to get locked in on New York by limiting her responsibilities away from the court.

"I'm really trying to stay away from stress and stay away from press," Williams said. "But, you know, that's a little difficult.

"I don't necessarily want to hear about, `Oh, this history and that history,' because I just want to be able to do the best that I can. I want to be able to win and I don't want any distractions. That's how I'm going to handle it."

The top-ranked Williams was coming off a loss to Belinda Bencic on Saturday night in Toronto in the Rogers Cup semifinals.

Williams' sister, Venus, dropped out of the tournament Tuesday night with an illness. Maria Sharapova also dropped out with a lingering injury to her right leg.

Third-seeded Simona Halep advanced, but fifth-seeded Caroline Wozniacki lost to Victoria Azarenka 6-0, 6-4. Azarenka, making a comeback from ankle and knee injuries last year, won 16 of the first 21 points to take control.

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On the men's side, Djokovic waited out a long rain delay before his match started, and then wasted chances to close it out quickly. He converted only 5 of 15 break points. The first set lasted 64 minutes, with Paire using drop shots to keep Djokovic guessing.

"It was a strange match all in all, but the instructions I got from the coach was to expect the unexpected, and that was the case," Djokovic said. "You couldn't really predict what kind of shot comes your way."

Djokovic has never won in Cincinnati, losing the finals to Andy Murray in 2008 and 2011, and to Roger Federer in 2009 and 2012. A title this week would make him the first player to win all nine ATP Masters events.

Murray, who beat Djokovic to win in Montreal on Sunday, beat Mardy Fish 6-4, 7-6 (1) in a match featuring a flurry of service breaks. There were four late in the second set, with Murray breaking Fish to tie it 6-6.

They traded points in the tiebreaker before Murray ran off six in a row to close it out.

"He made it very tricky for me," said Murray, who will face Bulgaria's Grigor Dimitrov on Thursday. "The conditions were tough. It was very humid."

Nadal knocked off Jeremy Chardy 6-3, 6-4 in a match that ended at 12:43 a.m. Chardy fought off four match points before Nadal finished it off. He'll play Feliciano Lopez on Thursday.

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