MELBOURNE, Australia -- It's rare that a Wimbledon champion air swings on an overhead.
Then came the kind of embarrassing mistake that only occasional players are supposed to make. Ivanovic hit a high defensive lob that barely cleared the net and Kvitova misjudged the ball, swung and missed.
The air swing, which allowed Ivanovic to pull to 4-5, seemed to throw the No. 2-ranked player off her game. She lost the next eight points to fall behind 6-5 -- badly missing on a couple groundstrokes -- and only managed to force a tiebreaker with two big serves out wide in the 12th game.
Kvitova righted herself in the tiebreak, however, showing why she's one of the favorites to hoist the Australian Open trophy on the weekend. Her shots started glancing off the lines again, and after hitting a backhand winner to go up 4-1, she let out a high-pitched shriek, doubled over and clenched her fist.
"You know, it was really easy point. I missed it. Actually I don't know why, what's happened," Kvitova said of the botched overhead after the match. "It was tough to get back and be focused on every point when I served. ... But, yeah, fortunately I did it."
In the end, she won 6-2, 7-6 (2) to advance to her second straight quarterfinal at Melbourne Park. She plays unseeded Sara Errani next for a chance to reach her third Grand Slam semifinal.
She's inching closer to another big prize, as well: Caroline Wozniacki's No. 1 ranking.
Wozniacki can hang on to it if she outperforms Kvitova here -- Victoria Azarenka and Maria Sharapova are also still in contention -- but Kvitova has the edge based on her two big wins last year, Wimbledon and the year-end WTA championship.
Martina Navratilova, who is playing in the legends doubles event at Melbourne Park, believes Kvitova will not only be No. 1 soon, she'll dominate the game for some time to come.
"Her attitude is fantastic," said Navratilova, who won her ninth Wimbledon title a few months after Kvitova was born in 1990. "Today she hit a whiff on the overhead, embarrassed as heck. Shanked like six balls in a row, but got it together, held serve.
"In years past, and even last year, she would lose those matches or lose her concentration. But now she gets it back together. She's tough."
Kvitova's power and toughness were on full display against former No. 1-ranked Ivanovic, the 2008 Australian Open finalist who is trying to find her form again after her ranking tumbled to 65th.
Ivanovic is still one of the toughest competitors in the women's game, but she had no answer for Kvitova's heavy groundstrokes, which she consistently hit deep into the corners, or the 6-foot (1.83-meter) Czech's booming serve.
Kvitova frequently surprised Ivanovic by returning the ball faster than the serves she was facing. She finished with 30 winners in the contest, twice as many as Ivanovic.
"You really have to get that hit on the ball, otherwise she likes to dominate and step up and take her chances," Ivanovic said after the match. "She's a good player and No. 2 for a reason."
Navratilova said she thinks the 21-year-old Kvitova is playing better than any of the other power-hitters in the game right now, which she attributes to an offseason workout program that has boosted the Czech player's fitness level.
"I'm glad I'm not the on the other side of the net," she said.