Serbia lost both reverse singles matches to Belgium on Sunday after it qualified for the Davis Cup quarterfinals a day earlier.
With top-ranked Novak Djokovic not playing Sunday, Belgium took advantage. David Goffin beat Boris Pashanski 6-4, 2-6, 6-2, and Steve Darcis defeated Nenad Zimonjic 6-2, 6-2.
The two losses left Serbia with a 3-2 victory. It will face the winner of the series between Brazil and the United States.