Tashkent, Uzbekistan (UzDaily.com) -- South African Raven Klassen ranked 244 scripted one of the biggest upset of the day as he knocked out top seeded Yen- Hsun Lu of Taipei, while 170th ranked Estonian Jurgen Zopp upset fourth seeded German Cedrik - Marcel Stebe and unseeded 191th ranked Russian Konstantin Kravchuk scored over eighth seeded Rik De Voest to enter the quarterfinals of the $125,000 Tashkent Challenger an ATP tour event.

In the second round matches played at the Olympic School Tennis courts here today the maverick Klassen scored a 6-4, 6-3 win over the top seed and world ranked 69th player Lu in 1 hour and 12 minutes, while 170th ranked Zopp scored a creditable 7-6(5), 7-5 win over fourth seeded and 107th world ranked player Stebe in 1 a hour and 43 minute tussle. In the longest match of the day unseeded Russian Konstantin Kravchuk upset the eighth seeded South African Rik De Voest 5-7, 6-3, 6-3 in a 2 hours and 33 minute battle to enter the last eight stage.

Local star and third seeded Denis Istomin who is the only remaining seeded player in the event scored a 6-4, 6-3 win over German Sebastian Rieschick.

In the biggest upset of the day Raven Klassen ranked around 160 places below the top seeded Lu played percentage tennis to upset the top seed Lu 6-4, 6-3 in 1 hour and 12 minutes and make it to his second Challenger quarterfinal this year.

"I played confidently and under no pressure at all, it's a great win for me," said Klassen who is gathering up quite a following here." None can deny Lu's class, he seemed to be off colour today," added Klassen. Klassen broke Lu in the 9th game of the first set and then in the 3rd and 9th games of the second set to make it to the last eight.

In the quarterfinals he will take on another unseeded player Ukranian Denys Mulchanov who came back from being 2-4 down in the third set against Indian wild card Vishnu Vardhan. Mulchanov managed to survive and win 6-7(4), 6-3, 7-5 in a match lasting 2 hours and 28 minutes.

Unseeded Jurgen Zopp of Estonia, registered a second consecutive win over fourth seeded German Cedrik-Marcel Stebe in as many weeks to make it to the last eight stage, Zopp who won against Cedrik at Ningbo last week after being 6-3, 4-1 up before the German retired, scored a 7-6(5), 7-5 win in 1 hour and 43 minutes.

The Estonian who started the year at 219 in rankings before moving to 170 currently traded 2 breaks apiece before forcing a first set tie break, which he won (7-5), in the second set Zopp broke Stebe in the 11th game and then held on to win the set 7-5 and make it to the last eight stage.

Zopp will take on one of the youngest player at the event Tsung Hua Yang of Taipei, who showed great character in overcoming Uzbek Davis Cupper Farrukh Dustov, scoring a 4-6, 6-1, 7-5 win in a well contested match lasting 1hours and 56 minutes.

Yang former top world junior star was broken in the 5th game of the first set, after Dustov fired a flurry of winners, to take the set at 6-4. in the second set Yang looked much relaxed and just gave away 17 points, breaking the Uzbek star in the 4th and 6th games to take the set 6-1 and level set scores.

In the third set Yang broke Dustov in the 3rd game and raced to 4-2 lead, but Dustov broke back in the 8th game to level scores at 4-4. Yang got the decisive break in the 11th game as Dustov made three unforced errors in a row to go down a break. Yang who fired 8 aces in the match served brilliantly to finish the match and make it to the quarter finals.

Wild card Murad Inoyatov seemed to be riding his luck further as, he led 6-1, 2-1 before giant killer Dominik Meffert retired from the match after 40 minutes, Inaytov made it to the quarterfinals of the challenger at home and will take on country mate and third seeded Denis Istomin.

Istomin who came out of thriller yesterday, seemed much composed and relaxed registering a rather easy 6-4, 6-3 win over another German Sebastian Rieschick in 1 hour and 04 mins. Istomin broke the Greman in the 10th game of the first set and the second game of the second set.

Russian Denis Matsukevich also seemed to go the Inoyatov way riding his luck into the quarterfinals as Czech player Jan Hernych retired after losing the first set 6-3, and down 1-0 in the second set.

Matsukevich will play country mate Konstantin Kravchuk who upset the eight seeded South African Rik De Voest 5-7, 6-3, 6-3 in the longest match of the day lasting 2 hours and 33 mins. Kravchuk came spledidly fom behind to break the South African Davis cupper in the eighth game in the third set and then holding on to finish the set 6-3.

In the biggest upset in the doubles event Uladzimir Ignatik of Belarus and Denis Matsukevish of Russia toppled top seeds Mikhail Elgin and Teymuraz Gabashvili 6-3, 3-6, 10-6 to enter the semi finals

Following are the results

Men’s Single 1st Round:

Murad Inoyatov (Uzbekistan) – Dominik Meffert (Germany) 6/1/, 2/1 Ret’d

Denis Matsukevich (Russia) – Jan Hernych (Czech) 6/3, 1/0 Ret’d

Denys Molchanov (Ukraine) – Vishnu Vardhan (India) 6/7(4), 6/3, 7/5

Jurgen Zopp (Estonia) – Cedrik-Marcel Stebe (Germany) 7/6(5), 7/5

Tsung-Hua Yang (Chinese Taipei) – Farrukh Dustov (Uzbekistan) 4/6, 6/1, 7/5

Raven Klaasen (RSA) – Yen-Hsun Lu (Chinese Taipei) 6/4, 6/3

Denis Istomin (Uzbekistan) – Sebastian Rieschick (Germany) 6/4, 6/3

Konstantin Kravchuk (Russia) – Rik De Voest (RSA) 5/7, 6/3, 6/3

Men’s Double 1st Round:

Uladzimir Ignatik (Belorussia) /Denis Matsukevich (Russia) – Mikhail Elgin (Russia)/Teymuraz Gabashvili (Russia) 6/3, 3/6, 10/6

Murad Inoyatov (Uzbekistan)/Sergei Krotiouk (Russia) – Farrukh Dustov (Uzbekistan)/Sander Groen (Netherlands) 6/4, 7/6(5)

John Paul Fruttero (USA)/Raven Klaasen (RSA) – Divij Sharan (India), Vishnu Vardhan (India) 7/5, 6/1