Fallout from the handshake snub

The boos Tomas Berdych received after refusing to shake Nicolas Almagro's hand in his last match might still be reverberating in the Czech's ears when he walks out for this quarterfinal against Rafael Nadal. Will he be able to put it behind him? Berdych once was known for his mental fragility but has improved over the last couple of years. This will be yet another test of that.

Upset after being hit in the arm by a running passing shot from Almagro, Berdych turned his back and did not look at his opponent's apology. Afterward, he dodged the customary postmatch handshake. The crowd showed their displeasure, jeering loudly all the way through Berdych's courtside interview.

Berdych maintained that Almagro should have aimed elsewhere, but backpedaled on his handshake decision after digesting the crowd's reaction.

"Maybe we both did some mistake. So it's even, and that's it," Berdych said.

But that may not be completely it as far as Nadal is concerned, because Almagro is a friend and fellow Spaniard, and the incident likely evoked memories of Nadal's own run-in with Berdych at the Madrid Masters in 2006, then played indoors. Unhappy with the level of partisan support Nadal received, Berdych shushed the crowd afterward, prompting Nadal to call him a "bad person."

Berdych played this down as well: "This is something what is maybe, what, five, six years old. Is nothing to talk about," he said.

But Berdych had also become annoyed during their match in the 2010 World Tour Finals in London when Nadal argued with the umpire about whether a point should be replayed. The umpire "is probably scared of him and allowed him talk too much," Berdych said at the time. But he stressed that he blamed the umpire: "Don't do anything that I said something against Rafa."

Nadal knows what that's like, having begun this tournament trying to backtrack on comments he made about Federer's position on tour matters.

This surface friction, however, may not be as important as the on-court psychology between the two, who go back to the juniors. Nadal leads their main tour head-to-head 10-3 and has won the past nine matches. Berdych's last win was that controversial match in Madrid. Before that, though, the Czech had won three of their first four tour matches, and all three were played on hard courts, continuing the edge he had built up in the juniors. What changed? Nadal now plays much more aggressively, says Berdych, making it harder for the big-hitting 2010 Wimbledon runner-up to take charge of the rallies.

That's why it will be particularly important for Berdych to try to get off to a good start and build an early lead and try to trigger Nadal's old Madrid memories (the tennis, not the controversy). But that will be more difficult in these conditions, with the match likely to be played on a hot day and Nadal's ball leaping off the hard court.

As for Nadal, his challenge is to remain aggressive, something he can struggle with when injuries or self-doubts surface. Of all the pieces in this mental chess match, that is the one to watch. Until the handshake, of course.

Prediction: Nadal in four

Roger Federer versus Juan Martin del Potro

This will mark Federer's 1,000th tour match, a milestone that comes against the most accomplished member of the upcoming generation: del Potro, the 2009 U.S. Open champion and the only player in the past six years to break the Federer-Nadal-Djokovic stranglehold on the majors. That means serious danger for Federer, because del Potro's emphatic victory in the previous round indicated that he is fully firing once again after his wrist problems. The meeting is expected to be closer to their famous five-set meeting in the 2009 U.S. Open final than their last meeting in Melbourne, when Federer floated to a 6-3, 6-0, 6-0 victory in the 2009 quarterfinals.

Del Potro hedged on his chances, saying, "I only won three games last time, so if this time is something different and I win more games is going to be OK for me."

Don't be fooled: This match is not expected to be anything like a rerun. "No, it won't. I can guarantee you that," Federer said. "I think it's going to be a good match. He really came through convincingly in the last two, especially. And, yeah, we know the firepower."

Federer has been on a roll since the U.S. Open and looked sharp against Bernard Tomic in the previous round, but may have to play even better to contain Delpo, who will likely swing freely and who happens to be one of the few players who can hit Federer off the court. That won't leave Federer much time to think about No. 1,000. "Obviously for me, it's just another match, but I know it's special in some ways," he said. "I will try to make the best of it, I guess."

Prediction: Federer in four

Caroline Wozniacki versus Kim Clijsters

There were some big words from Caroline Wozniacki coming into this match. "I don't think I have to play better," she said. "I think I just need to play my game and play the same way as I did today. If I do, Kim really needs to play well to beat me."

But the biggest factor will likely be the state of Clijsters' ankle. She twisted it during her fourth-round match but somehow found a way to play on it and saved four match points to get through. If the problem lasts, Clijsters will find it difficult to defeat Wozniacki's dogged counterpunching on one leg.

But if the Belgian is able to play unhampered, she's favored to hit through Wozniacki the same way she has in both their previous two meetings.

Prediction: Wozniacki in three

Victoria Azarenka versus Agnieszka Radwanska

There is growing talk of Azarenka possibly winning her first Grand Slam title in Melbourne, and the Belarussian has been looking fit and focused while rolling her way through the draw. But Radwanska is just the kind of player who can throw off a player's rhythm, and after nearly losing in the first round, plans to make a big try for her first Grand Slam semifinal.

This faceoff between power and finesse is a bit of a tossup, but Azarenka seems to believe in her chances at this event and might be a little tougher at closing time.

Prediction: Azarenka in three

Kamakshi Tandon is a freelance tennis writer for ESPN.com.