Can Venus play through pain?

MELBOURNE, Australia -- What will Venus Williams have left?

The seven-time Grand Slam champion showed ample heart in the second round at the Australian Open, overcoming a groin injury and an opponent with little to lose. Williams meets Andrea Petkovic on Day 5 in Melbourne, and you can bet the crowd will be behind the hard-hitting German.

Women's match to watch: Venus Williams (4) versus Andrea Petkovic (30)

Oracene Price has seen her daughters play through pain before. In fact, at most majors recently, one or the other -- sometimes both -- has been banged up.

Williams' physical woes were there for all to see, and hear, in Wednesday's three-set win over Czech Sandra Zahlavova at Rod Laver Arena. Having entered the tournament with a questionable knee, Williams shrieked as she struck an overhead at the end of the first set. Her groin, or as she later specified, "psoas" muscle, was the problem, not the knee.

Williams kept going after taking a medical timeout, thereby maintaining a roughly 12-year streak of not retiring. Considering her futile non-grass Slam efforts since 2001, we would have expected the amiable Aussie crowd to be on her side, as it would have been if Kim Clijsters or Justine Henin were suffering. Williams, at 30, is in the latter stages of her career.

That wasn't the case.

Trying to serve out the match, Williams caught her ball toss, well within the rules and certainly not a breach of etiquette if it doesn't happen often. Several in the stands booed.

Even as Williams moved less than freely and let out another yell in discomfort as the match progressed, the majority rooted for the world No. 97.

"It doesn't surprise me at all," Price said. "That always happens. I'm used to it."

Is it disappointing?

"No, it's not disappointing," she said. "That's the way it is. That's a matter of fact."

But Williams was determined to win.

"When she came back from the injury timeout, I knew she wasn't going to lose because of the way she looked," Price said. "That look. That look. She just made up her mind."

How Williams recovers is predictably pivotal as she prepares to meet Petkovic, who has moved up the rankings in the past year. But it doesn't look good. Williams didn't practice Thursday, rehabbing instead. Organizers then gave her a night match at Rod Laver Arena on Friday -- following a men's encounter.

Petkovic, mind you, wasn't completely unscathed in a topsy-turvy, 2-6, 7-5, 6-0 win over British qualifier Anne Keothavong, as she dealt with blisters on her foot.

Prediction: Petkovic in two

Men's match to watch: Novak Djokovic (3) versus Viktor Troicki

Djokovic's 2010 turned around at the U.S. Open. He saved two match points against Roger Federer to reach the final, where he didn't disgrace himself against Rafael Nadal.

His first-round win over Troicki, a good friend and Davis Cup teammate, was the catalyst.

Trailing two sets to one and by a break, and suffering from the intense heat, Djokovic was on the edge. Troicki blinked, and Djokovic ended up winning in five.

Five months later, Troicki, who owns a powerful serve and solid backhand, is a different player. He won the deciding fifth match in the Davis Cup final against France, showing no nerves, and has somewhat predictably taken off.

Troicki reached the quarterfinals in Doha and the final in Sydney, losing to a chap named Gilles Simon.

"He's definitely on a roll, playing really well," said Djokovic, who survived a loss of concentration to beat Croatian Ivan Dodig in the previous round. "We grew up playing tennis [together], so it's going to be a tough third round definitely for both of us."

Probably tougher for Troicki, who is 1-6 versus Djokovic.

Prediction: Djokovic in four

Upset watch: Caroline Wozniacki (1) versus Dominika Cibulkova (29)

No one needs to tell Wozniacki that Cibulkova is trouble. Cibulkova, perhaps even bubblier than the Dane, emerged victorious in their tussle in Sydney last week.

This coming after an exhibition in Asia, in which Wozniacki struggled to get a feel for her new Yonex racket.

"Coming in from Hong Kong, playing Sydney, it's a bit difficult," Wozniacki, 5-2 against the former French Open semifinalist, told reporters.

Cibulkova, despite being only 5-foot-3 (and that might be generous) will be doing the dictating as Wozniacki retrieves.

Prediction: Wozniacki in three

Five-set lock: Nicolas Almagro (14) versus Ivan Ljubicic (17)

Talented, flaky Spaniard Nicolas Almagro has a hard time winning easily outside his favored surface of clay. Since the end of 2008, not including Roland Garros, he's won two straight-set matches at Slams.

Last year in Melbourne, Almagro, who's targeting a return to the top 10, went the distance three times. He added another five-setter to his Down Under dossier Wednesday against Igor Andreev.

Both players have big serves, which means a slew of tiebreakers is possible. All four of their head-to-heads have been straight-set affairs, meaning we're due for a marathon.

Prediction: Almagro

Ravi Ubha is a frequent contributor to ESPN.com.