Russia's third seed Mikhail Youzhny reached the last four of the St Petersburg Open on Friday when German Philipp Kohlschreiber retired from their quarter-final after losing the first set 6-4. The seventh seed said he was feeling unwell.
"At the beginning I felt OK but towards the end of the first set I started feeling more and more tired," said Kohlschreiber. "After I lost the first set I felt I didn't have much chance of winning so I decided to retire and not to get worse."