Huge test for Twitter legend Karlovic

MELBOURNE, Australia -- With remarks such as, "Finally arrived down under, after 14 hrs on the plane I got to wash thoroughly down under," Ivo Karlovic has acquired quite the following on Twitter.

To be more precise, as of Thursday afternoon in Melbourne, he had more than 23,000 followers.

"I think that for my ranking it's a lot," quipped Karlovic, the world No. 57.

The soft-spoken, 6-foot-10 Karlovic will likely attract a few more if he beats Roger Federer in the third round of the Australian Open on Friday.

He knows how difficult the task is.

The semifinal streak may be over, but Federer hasn't lost before the quarterfinals at a major since the 2004 French Open.

The Swiss holds a 9-1 head-to-head advantage over Karlovic and has beaten him in their two Grand Slam tussles without dropping a set. They were both at Wimbledon, where Federer countered Karlovic's serving missiles with crisp returns. Overall, Federer is riding a 21-match winning streak.

Still, Karlovic is relishing the opportunity to face the 16-time Grand Slam winner on the main Rod Laver Arena. Karlovic took on Rafael Nadal at the same stadium two years ago and, despite being ill, didn't disgrace himself. He extended Nadal to four sets.

"I'm excited because it's another match, and I will have an opportunity to win," Karlovic, 32, said. "It is another good experience."

Since topping Federer in Cincinnati in 2008, a result that knocked Federer off his No. 1 perch, Karlovic has lost all seven of their sets. The reason, he says, has a little to do with being passive in his returning. Oh, and Federer has played a part in it, too. He vows to let it rip Friday.

"I wasn't really risking a lot on the return games," said Karlovic, who rebounded from an Achilles injury that sidelined him for six months in 2010. "I was more just putting the ball in play, which against him, isn't the way. I have to risk a lot more and go for my shots, go to the net a lot."

Federer had an unexpected day off Wednesday when his second-round opponent, Andreas Beck, withdrew with a back injury. Whether that's a positive for Federer remains to be seen, although it probably won't have a detrimental effect, given that it's still early in the tournament. If anything, it allowed his own back to heal. Novak Djokovic's extra days off late during the French Open last year, some argued, threw him off ahead of his semifinal clash against Federer.

Federer was due, for the first time since 2004, to compete at the Australian Open on a court besides Rod Laver Arena.

"I would have loved to play," Federer said. "Feel sorry for the fans who were excited to see me on Hisense. I was ready to go."

Karlovic usually doesn't tweet about tennis. But that might change if he advances.

Prediction: Federer in four.

Alexandr Dolgopolov (13) versus Bernard Tomic

Grab some popcorn and a drink. This one should be plenty of fun: two of the most watchable, unorthodox players on the tour squaring off on Rod Laver Arena. Call it a taste of their own medicine, as they say.

"He's a very difficult player to play," Tomic said. "I think he doesn't like my game. I don't like his."

But the difference is that Dolgopolov has had the success in their head-to-heads, winning all three matches. Tomic tried to explain away their encounter in Shanghai in the fall (he lost 5-7, 6-1, 6-0), claiming he was put off when the match had to be moved indoors.

In Tomic's favor, however, is the fact that he continues to mature, and he'll have the crowd behind him. And he's high on confidence. Dolgopolov's health is also a question mark.

He suffers from Gilbert's syndrome, a blood condition that can cause fatigue, and he suspected that it manifested itself in his first-round match against another Aussie, Greg Jones. He admitted that he almost retired. Dolgopolov survived in five sets, but then went five more sets in the second round against Tobias Kamke, prevailing 8-6 in the fifth.

"First set today I was feeling also a bit tough, then I got better and better," Dolgopolov said Wednesday.

Tomic said he'd prefer to play at night -- and, of course, his wish was granted. Dolgopolov won't mind that, since he doesn't like the heat.

So much intrigue.

Prediction: Tomic in four.

Jelena Jankovic (13) versus Christina McHale

Christina McHale is a keeper.

The New Jersey native competes years better than the 19-year-old kid she is. She's unafraid to linger on court to get the job done, and her forehand is a weapon. McHale went deep again Wednesday, needing almost three hours to dispatch an almost-local favorite, Kiwi Marina Erakovic. As the years unfold, she'll want to lessen her court time.

But still in her youth, she should have plenty in the tank for Jankovic in what could be another marathon affair, given the Serb's style of play.

Their only encounter was quick, mind you, as Jankovic won 6-2, 6-0 on clay last year in Charleston. As bad as the score looks, it wasn't as lopsided as that.

This one must be closer.

Prediction: Jankovic in three.

London-based Ravi Ubha covers soccer and tennis for ESPN.com. You can follow him on Twitter.