Defending champion Caroline Wozniacki took 43 minutes to win her first-round match at the Pilot Pen then credited boxing with helping her score the quick knockout on Tuesday.

The second-seeded Wozniacki dominated Edina Gallovits of Romania 6-0, 6-0, winning 20 of the final 21 points in a 19-minute first set before taking 24 minutes to finish off Gallovits.

The Danish star, ranked No. 9 in the world, said her speed and fitness level began improving just after Wimbledon, when friend and super middleweight champion Mikkel Kessler suggested she take up boxing.

“You run a lot,” she said. “You get strength in your stomach, your back, your shoulders, your arms, all the things that you also need in tennis.”

So far, Wozniacki has hit mostly bags, sparring just once with her coach - and apologising after she punched him.

“He started yelling at me, ‘Why are you saying sorry? It’s what the game is about. You have to hit me,”’ she said. “It’s just fun to get some aggression out some times.”

While Wozniacki barely worked up a sweat, Samantha Stosur needed almost 3 hours to beat Frenchwoman Alize Cornet. The Australian ended up losing the first set after nearly 90 minutes, but won 6-7 (8), 6-2, 6-4.

“It was a bit of a battle out there,” Stosur said. “I got through the second set pretty quick and then started to feel better about things. The third was pretty tight. I was pleased with the way I was able to get out of it and come back from a set down.”

Amelie Mauresmo, a finalist four years ago, advanced with her first win over Alona Bondarenko of Ukraine in three attempts at 6-1, 6-1, sixth-seeded Marion Bartoli defeated Maria Jose Martinez Sanchez of Spain 4-6, 6-3, 6-1, and third-seeded Flavia Pennetta had a much easier time, defeating Ioana Raluca Olaru of Romania 6-1, 6-2.

In the men’s draw, Nikolay Davydenko won a 22-point tiebreaker in the first set and went on to beat American Robert Kendrick 7-6 (10), 6-3.

Davydenko struggled with Kendrick’s serves, which occasionally topped 130 mph (209 kph), giving up a dozen aces. But he used a strong backhand return while leading 11-10 in the first set tiebreaker that Kendrick put into the net.

“He put it right at my feet,” Kendrick said. “I should have served to his forehand.”

The eighth-ranked Davydenko broke Kendrick at love to go up 5-3 in the second set and served out the match. After missing most of the spring with a heel injury, he said he’s trying to do more than just get his game in shape for next week’s U.S. Open.

“For me, it’s important winning matches also here,” Davydenko said. “If I’m winning (the) tournament, I’m making points here. ... For me, it’s important for the ranking.”

Second-seeded Fernando Verdasco of Spain also advanced with a 6-0, 6-3 win over Paul Capdeville of Chile. Third-seeded compatriot Tommy Robredo wasn’t as fortunate, losing to Jose Acasuso of Argentina 3-6, 7-5, 7-6 (5).

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