World number one Novak Djokovic has pulled out of his Davis Cup quarter-final singles rubber against Sweden's Ervin Eleskovic due to a knee injury.
The Wimbledon champion will be replaced by Janko Tipsarevic, who will face Ervin Eleskovic.
No decision has yet been made regarding Djokovic's participation in Sunday's singles, when he is scheduled to face Michael Ryderstedt.
Viktor Troicki gave Serbia an early lead when he overcame Ryderstedt in four sets in the opening match on Friday.
Tipsarevic then but Serbia into a 2-0 lead when Eleskovic retired while 2-6 0-1 down in their rubber.