Russia have suffered a huge setback to their Davis Cup hopes after Nikolay Davydenko and Mikhail Youzhny retired with injuries at the St Petersburg Open yesterday.

Top seed Davydenko quit his second-round match against South Africa's Wesley Moodie with a foot injury while leading 6-2, 3-3.

Just 30 minutes earlier, eighth-seeded Youzhny pulled out of the $1 million tournament after spraining his right ankle in a doubles match. Swede Thomas Johansson received a walkover into the singles quarter-finals as a result.

Russia host Argentina in the Davis Cup final from December 1st-3rd in Moscow.

"I hurt my right foot in the seventh game of the first set when I ran for a short ball," Davydenko said. "I just felt a huge pain in my foot. I don't think it was my ankle, it was more like my heel.

"I called a trainer after the next changeover to tape my foot.

"I won the first set, but in the second I felt more pain and had trouble moving around the court.

"I probably could have continued but I wasn't sure how I would feel tomorrow and I just didn't want to take any chances with a Masters tournament in Paris coming up next week and the (season-ending) Masters Cup in Shanghai to follow."

Youzhny's injury appears to be more serious. The world number 23 was taken to hospital for X-rays.

"Medical tests will show if Youzhny would be able to participate in any future tournaments for the rest of the year," ATP officials said in a statement.

"I didn't even know Mikhail was injured until his coach Boris Sobkin told me just after my match," Davydenko said. "I don't know the extent of his injury but I hope both of us will be able to play in the Davis Cup final. There's still a lot of time left."