Huge hurdle to climb for Petrova

MELBOURNE, Australia -- The third round is when things start to get a little serious, given seeds start running into each other. Darling Kim Clijsters, on a roll and with the Aussie crowd behind her, figures to be tested somewhat against the unpredictable Nadia Petrova on Day 5.

Kim Clijsters (15) versus Nadia Petrova (19): Petrova was in good spirits as she practiced with coach Christian Zahalka on Court 20, nestled parallel to train tracks and well away from the crowds. Intermittent breezes tempered the intense warmth Thursday.

Petrova let out a few smiles as she worked on returns and skied a ball onto another court, proclaiming it was a home run.

The 5-foot-10 Russian needs to hit one out of the park to oust Clijsters, riding a nine-match Grand Slam winning streak and coming off a confidence-boosting victory over Justine Henin in the final of the Brisbane International.

"Nadia has to serve well," said Zahalka, the latest in a long line of Petrova coaches. "If she serves well, and if every set is tight, anything can happen. She has to be aggressive. She has to take it to Kim and dictate. If she can do that, she has a shot."

Petrova, whose serve is one of the biggest in the women's game, can't help running into Belgians. She faced Henin, on the comeback trail, in an exhibition in Cairo last month and, as the No. 2 seed, unfortunately drew the seven-time Grand Slam winner in the opening round of the Brisbane International. It was a close affair, with Henin prevailing 7-5, 7-5.

"It was a very tight match, a winnable one," said Zahalka, who has been in Petrova's corner for six months. "Justine won the match, not Nadia losing it."

Petrova was once a Grand Slam contender herself, even though she isn't especially mobile. In 2006 the Muscovite won three straight clay-court titles, downing Henin in the process, and was considered the favorite at that year's French Open. The week before Roland Garros, however, Petrova injured her ankle and she exited in the first round. The 27-year-old, ranked third in May '06, has never really recovered.

"I'd much rather face Clijsters or Henin in the semifinals, I admit that, but for us the ranking isn't important," Zahalka said. "She wants to be in the mix again, and that's the only [reason] I took the job. You gotta beat girls like Clijsters to do it, so let's go do it."

Clijsters, 4-0 against Petrova with a single set lost, played sloppily against veteran Thai Tamarine Tanasugarn in the second round. The reigning U.S. Open champion almost blew a big lead in the first set and fell behind 3-0 in the second.

Petrova is a clear step up.

"She obviously has a great serve," Clijsters told reporters. "Places the ball well, hits it very clean. I have to try to be consistent, but really try to go for the lines and make her move because she's a tall girl. Usually tall girls, they're not the greatest movers around."

Prediction: Clijsters in three.

Rafael Nadal (2) versus Philipp Kohlschreiber (27): Kohlschreiber, a diminutive German, has a bit of a fan club in Australia. It all stems from his explosive performance against Andy Roddick in the third round of the Australian Open two years ago. Kohlschreiber hit a century of winners to eliminate an out-of-sorts and grumpy Roddick 8-6 in the fifth.

Kohlschreiber, given his enormous talent, has since underachieved. He has yet to reach a Grand Slam quarterfinal and has a tendency to lose matches he probably should win.

No favorite here, Kohlschreiber trails Nadal 4-0 in their head-to-heads, although in their last meeting in Dubai in 2008, the 26-year-old pushed the Spaniard to three sets.

Prediction: Nadal in four.

Gael Monfils (12) versus John Isner (33): The 6-foot-9 Isner, along with Sam Querrey, is the immediate and bright future of U.S. men's tennis.

Isner is on a roll, winning his first title in New Zealand last week, aces in tow, and pulling out a five-set win in the first round in Melbourne. Admitting to being fatigued this week, he got some much-needed rest Thursday. He also owns a 2-1 record against the elastic Frenchman.

"I'm going to have to serve well and get into the net," Isner told reporters. "I probably don't want to get into long, extended rallies with him."

Monfils' shoulder was a question mark last week, but his coach, Roger Rasheed, says it's fine now.

Prediction: Monfils in five.

Ravi Ubha is a frequent contributor to ESPN.com.