MELBOURNE, Australia -- Serena Williams' biggest challenge so far in trying to secure a third consecutive major title and reclaim the world No. 1 ranking has been staying out of her own way.
A rolled ankle suffered in a steamroller of an opener didn't appear to trouble Williams in Thursday's second-round Australian Open match against rangy, 6-foot-tall Garbine Muguruza of Spain, but the third-seeded Williams looked unhappy anyway during stretches of the 6-2, 6-0 win after accidentally swatting herself in the mouth with her racket, splitting her upper lip.
"I think it happens to everyone, but I have never busted it wide open like that," a sheepish Williams said afterward. "So, yeah, I was like, 'Oh, no. I can't have a tooth fall out. That would be horrible.'
"I don't know why my racket was even in my face. I mean, it's like I have been playing tennis far too long to hit myself. ... I'm like, 'Come on.' Like, 'Serena, pull yourself together here,' you know."
As ESPN analyst Pam Shriver noted, there was a lot of force behind that mishit.
"I wouldn't want to get hit in the mouth with her racket," Shriver said. "It sounds like death."
In stifling 100-degree heat at Rod Laver Arena, the Venezuelan-born Muguruza struggled with her serve and could only watch at times as Williams pounced on her second delivery. But Muguruza hung in gamely through some lengthy service games, including the 18-minute one that started the second set.
"I actually thought she improved as the match went on," Williams said. "She was blasting balls for winners and she has a pretty big serve."
Williams, a five-time champion in Melbourne aiming for her 16th Grand Slam event title, appeared increasingly mobile as the match progressed and cracked a 128 mph ace on match point.
She said her right ankle -- twisted in the first set of her opening match -- was still tender during an indoor hitting session Wednesday but "so far, so good. I felt pretty much better than I ever dreamed of expecting to feel."
Meanwhile, another American player booked an appointment with the woman considered to be Williams' biggest impediment to a sixth Aussie Open championship.
Alabama native Jamie Hampton -- who said she's in shape for success after a demanding offseason at the U.S. Tennis Association training center in Florida -- won her second straight lopsided contest and advanced to the third round, where she'll face defending champion and world No. 1 Victoria Azarenka.
The blunt, understated Hampton, who turned 23 earlier this month, said she's happy to have a chance to face a big-time player on a big show court and erase the memory of last year. She came through the qualifying tournament and won her first-round match only to be "thumped," in her words, 6-0, 6-1 by Maria Sharapova.
Now ranked 63rd in the world, Hampton said she got her early-season nerves out of the way this year in Auckland, where she played a tough, confidence-building match against No. 4 seed Agnieszka Radwanska of Poland, losing 7-6 (4), 7-6 (3) in the semifinal. She has never played Azarenka but said she knows to expect a physical contest.
"She moves really well and neutralizes points pretty easily," Hampton said.
Hampton was serving for the match up 6-1, 5-0 against qualifier Luksika Kumkhum of Thailand when the slender 19-year-old began to put more balls in play on the quick outer court and delayed the inevitable for a while. But Hampton closed things out in the second set 6-2, gave a little fist pump, packed up and left the premises with a quick, purposeful stride.
ESPN analyst and U.S. Fed Cup captain Mary Joe Fernandez knows Hampton well from having included her on the American team as a practice partner several times and said Hampton has matured slowly but is fully capable of testing Azarenka if she can stay positive.
"She's strong, she's a great athlete, she has a world-class double-handed backhand and a really nice one-handed slice, really efficient," Fernandez said. "Can volley really well. The forehand is the one shot she's been working on. It's more mental than anything else with her, not getting down on herself. She's really hard on herself, so she's learning to move on to the next point and put it past her.
"She'll go out there believing she can win. She's ready for these type of matches."
Williams -- who intends to stay in the doubles draw with her sister Venus -- next faces No. 72 Ayumi Morita of Japan and will try to avoid any more flukes in her march through her unthreatening corner. If she reaches the final here, she will become the oldest-ever world No. 1.
"I have done this more times than the average person, so I should be OK," she said.