St. Petersburg, Russia:
Top-seeded Mikhail Youzhny of Russia retired with lower back pain while trailing Denis Istomin of Uzbekistan 6-2, 2-1 on Thursday in the second round of the St. Petersburg Open.
Trailing 5-2, 30-15 on his serve in the first set, Youzhny double-faulted. He saved one set point but then returned wide to loose the set. He took a medical time out to have his back massaged but trailing 2-1, 15-40 in the second set he decided to retire.
Youzhny said he would decide if he would play at the Valencia Open next week after a medical exam.
In his second quarterfinal this season, Istomin, who has yet to win a title, will either face fourth-seeded Igor Andreev or two-time champion Marat Safin.
Earlier, Ukrainian qualifier Sergiy Stakhovsky beat Russian wild card Andrey Kuznetsov 6-1, 6-4, and Igor Kunitsyn defeated wild card Michail Elgin 6-2, 6-3 in an all-Russian match.
Stakhovsky broke Kuznetsov, the Wimbledon junior champion, three times to reach the quarterfinals of a tournament for the second straight week. He lost to Youzhny at the Kremlin Cup last week.
Stakhovsky will play German veteran Bjorn Phau, while Kunitsyn will face second-seeded Victor Hansecu of Romania