By Kamakshi Tandon

Serena Williams (USA) vs. Nicole Vaidisova (CZE)[10]Rod Laver Arena - 2nd match

It’s a dangerous floater versus a seed in this match, but the labels don’t apply quite the way you’d expect them too. Williams has passed all the tests she’s faced at this Australian Open – tricky early round matches, top seeds, mid-ranked but in-form battlers. This is yet another one: a big-hitting youngster she's never played before. It’s clear now that Williams is playing at a very high level, with the only question being whether she can physically sustain the pace with so little play under her belt.

For all the temptation to focus on Williams in this match, it’s also an important one for Vaidisova. In her second Slam semi, she should be determined to win the match and declare her own career ambitions in the process – a tame loss would send the wrong message. There’s also the ever-present question: can Vaidisova hold it together mentally? She’s done it so far, but hasn’t had to deal with anything like Williams’ intensity until now.

Mark the Czech teenager as the underdog, but definitely not to be written off. A two-set win is more likely than a three-set win, however.

Predicition: Unforced errors.

Maria Sharapova (RUS)[1] vs. Kim Clijsters (BEL)[4]Rod Laver Arena - 3rd match

The semifinal everyone has been waiting for, and the virtual final in some eyes. Clijsters would have been the favorite coming in, but her surprisingly erratic performance against Hingis – 62 unforced errors – dilutes that status a bit. Her early-round matches had been very quick, but playing non-stop since the beginning of the year (winning a Hong Kong exhibition tournament and the WTA event in Sydney) may be starting to have a mental impact.

Sharapova came through her last match in straight sets but still took over two hours to finish. Though it was nowhere near as hot as it was during her first-round match, her shoulders still turned red in the sun and she reapplied sunscreen on the changeovers.

Unlike the other two semifinalists, the two will be playing for the second day in a row. It's their seventh meeting –Clijsters leads the head-to-head 4-2 but has lost the last two encounters. If Wednesday was just a temporary lapse, Clijsters should outrun and outlast Sharapova in most of the rallies. But if Clijsters really has hit the wall, Sharapova will find enough in the tank to pull through. And dad Yuri will hopefully sit on his hands this time.

Prediction: The crowd will be pulling for ex-Aussie Kim to come through in her last Australian Open.

Roger Federer (SUI)[1] vs. Andy Roddick (USA)[6]Rod Laver Arena - 4th match

Roddick is looking very good these days. Trouble is, Federer is looking even better. Can Roddick make it interesting? Very possibly. Can Roddick win three sets against the Federer Express? Very unlikely, but it’s going to be fun to watch him try. And he will try.

Prediction: Hype.