MELBOURNE (AP) ― Apart from a swollen lip that helped take her mind off her injured right ankle, Serena Williams emerged unscathed from her second-round win at the Australian Open on Thursday.

Summoning all her experience from 15 major titles, including the final two of the last season, Williams lifted her tempo on the biggest points ― winning an 18-minute game to open the second set, finally cashing in on her fourth break chance.

Nineteen minutes later, she finished off a 6-2, 6-0 win Thursday over No. 112-ranked Garbine Muguruza with an ace at 128.7 mph ― the fastest she can remember serving.

“I’m on the up and up, I feel. It can only get better from here,” she said, adding that she wasn’t bothered by the ankle problem that caused concerns during her first-round win.

“Obviously when you go out to play you’re heavy on adrenaline and you’re really pumped up,” she said. “Usually I feel injuries after the match but so far, so good. I felt pretty, much better than I ever dreamed of expecting to feel.”

Williams couldn’t explain how she hit herself in the face with her racket in the sixth game, a blow that left her bleeding from the lip.

“But it’s OK,” said Williams, who played cautiously and kept most points short. “It’s a war wound.”

“I think it happens to everyone, but I have never busted it wide open like that. So, yeah, I was like, ‘Oh, no. I can’t have a tooth fall out.’ That would be horrible.”

With temperatures high late Thursday, defending champion Victoria Azarenka made sure she wasn’t on court long.

The top-ranked Azarenka practically danced into Rod Laver Arena for the first match of the day, and said she’s starting to find some rhythm after beating Eleni Daniilidou 6-1, 6-0 in 55 minutes.

“I felt like I’m back into the competitive mode,” she said. “I was really focused ― that was for sure the best part of the game for me.”

The No. 94-ranked Daniilidou only won 10 points in the first set and was shut out in the second despite having triple break point in the fourth game.

Azarenka had her friend and musician RedFoo in the stands watching and signing autographs, and said she went onto the court listening to a “great mix of disco music and a little bit of new music. I really start to like it a lot ― there’s no words really.”

The 23-year-old Belarusian won her first Grand Slam title in Melbourne last year, during a 26-match winning streak to start the season.

“It’s pretty difficult to duplicate something like that,” she said. “All I can do is try.”

Players wore ice vests and were shielded by umbrellas during the breaks in play as the temperature increased during Day 4 after three days of relatively cooler conditions.

The heat didn’t seem to bother 42-year-old Kimiko Date-Krumm, who advanced 6-2, 7-5 over Shahar Peer of Israel. She’s the oldest woman to win a singles match at the Australian Open.

Other women advancing included former No. 1-ranked Caroline Wozniacki, No. 14 Maria Kirilenko, No. 16 Roberta Vinci, No. 20 Yanina Wickmayer and Elena Vesnina, who beat No. 21-seeded Varvara Lepchenko of the United States 6-4, 6-2. Former U.S. Open champion Svetlana Kuznetsova beat 26th-seeded Hsieh Su-wei of Taiwan 6-2, 6-1.

U.S. Open champion Andy Murray had a 6-2, 6-2, 6-4 victory over Joao Sousa of Portugal. Murray, who ended a 76-year drought by British men in Grand Slam tournaments with his win at Flushing Meadows last year, didn’t allow Sousa a single break point chance.

“When the sun came out, it was extremely hot. When it wasn’t, it was fine. There was no humidity,” he said. “When you get the combination of the heat and the humidity is when it’s normally at its worst. I’ve played in worse conditions.

“But it’s still very hot. A good match to get done in straight sets.”

Australia’s Bernard Tomic went through to the third round with a 6-7 (4), 7-5, 7-6 (3), 7-6 (8) win over German qualifier Daniel Brands.