World No.3 Elena Dementieva and No.11 Caroline Wozniacki marked the start of the new tournament called the Mutua Madrilena Madrid Open by playing "Underground Tennis", the latest promo invention of Sony Ericsson.

Dementieva and Wozniacki played tennis on a specially built court placed on the unused track of the Chamartin Metro station, while commuters were passing by.

Here’s the video clip from the event.

Previously, Sony Ericsson promoted tennis with matches at other unlikely places like the terrace of Villa Miani in Rome, on top of cars, on water, and on a desert island.

Second seed Elena Dementieva and third seed Jelena Jankovic advanced to the quarterfinals of the Porsche Tennis Grand Prix in Stuttgart.

Dementieva played Agnes Szavay in the second round and despite being 4-1 behind in the first set, the Russian battled back to win the set in the tiebreak. Dementieva then cruised through the second set, but needed five match points to seal victory.

"I am still finding my feet on clay court. It is my first tournament of the year (on clay) and my footwork needs to improve," said Dementieva, who will next face Marion Bartoli, the winner over Caroline Wozniacki in the second round.

Defending champion Jelena Jankovic overcame Germany’s promising player Sabine Lisicki, who won Family Circle Cup this month, and beat 20th-ranked Patty Schnyder in the previous round in Stuttgart. The world No.42 Lisicki took Jankovic to three sets, but the Serb won 7-5 5-7 6-3 after two hours and 13 minutes of play.

Jankovic will encounter Flavia Pennetta or sixth seed Nadia Petrova in the quarterfinals. (photo: Ralf Reinecke)

Danish teenager Caroline Wozniacki added fourth seed Elena Dementieva to the list of top players who exited the tournament too early, which already includes Dinara Safina, Vera Zvonareva, Ana Ivanovic and Jelena Jankovic.

While the four women lost in the third round or earlier, Dementieva was a bit better,  falling to the WTA Tour's newcomer of the year 2008 7-5 6-4 in the fourth round.

The 18-year-old Dane, ranked 12th in the world, came back from a break down in both sets to reach her sixth quarterfinal of the season.

Wozniacki’s next opponent will be world No.8 Svetlana Kuznetsova, who comfortably won her match against fellow Russian Alisa Kleybanova 6-2 6-1. (source: Reuters, photo: Ralf Reinecke)

Jelena Jankovic’s bad results are becoming worrying. We know she’s struggling to bring her form back, but this latest second-round loss at the BNP Paribas Open is only deepening the despair.

The second-seeded Jankovic was upset by young Anastasia Pavlyuchenkova 6-4 6-4. The 17-year-old Pavlyuchenkova, ranked 42th in the world, scored her first Top 10 victory.

"Last year I finished No.1 in the world and I was playing great tennis, especially at the end of the year. This year I'm not the same player," Jankovic said. "I'm struggling to find my game and the confidence on the court. She played well. Obviously she was the better player. But I'm not at my level."

Third seed Elena Dementieva was also stunned, but her loss is much less worrying than Jankovic’s. Dementieva has won two WTA titles this year and overall has been amazing in 2009, so we can understand her tiredness.

Dementieva was erratic and hit 14 double faults before falling to qualifier Petra Cetkovska 7-6(2) 2-6 6-1 in the second round of Indian Wells.

"That was probably my worst match in a long time," Dementieva said. "Every time you lose you're trying to learn something. I feel I shouldn't have come here because I played a lot of matches at the beginning of the year, and I probably needed more time off to recover."

Ana Ivanovic didn’t suffer the same faith as Jankovic and Dementieva. After losing the first three games of the match, the fifth seed won 12 of the next 16 games and beat Belarusian qualifier Anastasiya Yakimova, 6-4 6-3. (source: Sony Ericsson WTA Tour, photo: Ralf Reinecke)

Amelie Mauresmo only had one win over a Top 10 ranked opponent in 2007 and 2008, but today she beat one of the most successful players this season Elena Dementieva 7-6(7) 2-6 6-4 and scored her fourth Top 10 victory in 2009.

Mauresmo, who advanced to the finals by defeating world No.10 Agnieszka Radwanska in the quarterfinals and world No.3 Jelena Jankovic in the semifinals, clinched her third title at Paris, having already won the tournament in 2001 and 2006.

"I have had hard times. I did some soul searching by the end of last year and there is a new dynamic, a good preparation during the winter," said eight-seeded Mauresmo.

Falling to the Frenchwoman, third-seeded Dementieva failed to score her 500th career win. (photo via Open GDF SUEZ)