The Serbs needed Djokovic to win to level the tie at 2-2 and he took a commanding two-set lead and was two breaks of serve to the good in the third. ut with a deciding rubber looking near certain, Davydenko clawed his way back to win the set and Djokovic promptly retired at 4-6, 3-6, 6-4 complaining of feeling dizzy and nauseous.
“I decided to stop as I didn't want to risk my health," said Djokovic.
“I wanted to fight. I tried to play but in the end I was aware of the fact that I was very dizzy and had no energy.
“I just didn't want to continue because of the risk."
Djokovic had missed his opening rubber on Friday against Mikhail Youzhny because of flu but returned to win Saturday's doubles alongside Nenad Zimonjic.
In the quarter-finals Russia will meet the Czech Republic, who beat Belgium.
VIENNA: Doubles specialist Bob Bryan put the seal on a crushing 4-1 victory over Austria yesterday to set holders United States off to an assured start in their Davis Cup defence.
After watching his twin brother and doubles partner Mike limp off after one set against Austrian number one Stefan Koubek with a left hamstring injury, Bob Bryan completed victory with a 6-0, 3-6, 7-6 win over Werner Eschauer.
Bob Bryan has now won three of his five Davis Cup singles but he ruled out any suggestions of launching a career in that form of tennis after beating a man ranked 58th in the world.
“After the first set, I thought 'jeez, maybe I should play singles again' but seriously, I don't think so," he told reporters. “I think it will take about two weeks to recover from this."
The US had made sure of an April quarter-final date against France on Saturday when the Bryan brothers, ranked world number one doubles pair, added victory to opening day successes for Roddick and James Blake.