Delpo + Sveta come undone Down Under

Fourth seed Juan Martin del Potro hid his head in frustration during his 5-7, 6-4, 7-5, 5-7, 6-3 defeat at the hands of Marin Cilic in the Aussie Open fourth round.

The towering Croat gained sweet revenge for his defeat at the hands of Delpo in the quarterfinal stage of last year's U.S. Open. He'll face Andy Roddick for a spot in the final four.

It was a breathtaking display of power hitting from every part of the court with each baller throwing in some slices and making quick forays into the net for good measure. I'd say Marin's focus and calm in the big moments made the difference here.

Svetlana Kuznetsova, the third seed, was also upset in the fourth round by her giant-killing compatriot Nadia Petrova 6-3, 3-6, 6-1.

Even though the Roland Garros champ traditionally struggles in Oz, Nads has been playing big ball this tourney and - I can't believe I'm saying this - has been toughing out opponents mentally. Her game hasn't let down even when it's been challenged the most.

But this new found mental strength will face it's biggest challenge when she takes on Justine Henin for a spot in the semifinals. The winner of this contest will be the fave from this half of the draw to get to the final.

In any case Nads should keep doing whatever she's been doing in her training on and off-court because it's working.

[Photo(s): Reuters, AP]