Fourth seed Nikolay Davydenko was forced to retire with a wrist injury in his second-round clash with Germany's Michael Berrer at the Dubai tennis championships on Wednesday.
The Russian looked out of sorts, losing the first set 6-3, having battled back from a set down on Tuesday to get into the last 16.
"It started yesterday afternoon," said Davydenko. "I was thinking: 'Okay there's pain, but I will recover'. I warmed up (today) and the wrist was feeling okay but the match was different and it started to get swollen."
The world number six is now a doubt for Russia's Davis Cup tie against India in Moscow next week.
Berrer, 29, dominated, breaking his beleaguered opponent in the fourth game after Davydenko had put a backhand smash into the net, and then held serve comfortably to clinch the set.
"I played very aggressive. I played the ball where it came from; he likes to play it from running," said Berrer, who has never made the world top 50. "I went to the net a lot, put pressure on the second serve."
The German has now won more ATP matches this year than he did in the whole of 2009 and he put this improvement down to his new coach, Claudio Pistolesi.
"(He's) given me a lot of confidence. I'm German and we're a little bit self critical and he's helped me to believe more in my strength," said the left-hander.
Berrer will now play Cypriot Marcos Baghdatis or Indian qualifier Somdev Devvarman in Thursday's quarter-finals.
Austria's Juergen Melzer beat Spaniard Tommy Robredo 6-3 7-5 to earn a last-eight clash with Marin Cilic after the world number nine wrapped up a routine 6-2 7-6 victory over another Austrian, Stefan Koubek.
Croatian Cilic was rarely at his best, making only 47 percent of first serves, and squandered six set points after racing into a 6-0 lead in the second-set tiebreak, eventually triumphing 8-6.
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