The world number two recorded victory in the ATP World Tour Finals on Monday to extend his streak to 22 matches but he insists that Serbia cannot afford to waste such a great opportunity.
"It's been a very long season for me and I'm exhausted in every way," Djokovic told reporters. "But God knows if as a country we are going to have another opportunity, another generation like this, to win a Davis Cup title at home.
"We have very tough opponents - the defending champions - but the Davis Cup is the only team competition in our sport that brings the best possible energy and will-power in me, and I speak for my team-mates, too. I'm going to do my best to recover in the next three days."
Janko Tipsarevic is a reported doubt for this weekend's final with a heel injury.