World number one Rafael Nadal beat number three Novak Djokovic 6-4 6-4 6-1 on Sunday to give champions Spain an unassailable 3-1 lead in their Davis Cup world group first-round tie.
Nadal and David Ferrer both won their opening singles in straight sets on Saturday, Ferrer upsetting an erratic Djokovic and Australian Open champion Nadal thrashing Janko Tipsarevic to put Spain 2-0 ahead.
Nenad Zimonjic and Viktor Troicki then beat Feliciano Lopez and Tommy Robredo, also in three sets, to keep Serbia alive ahead of the reverse singles.
The tie had been due to begin on Friday but play was postponed after high winds damaged the seating at the purpose-built arena around the clay court in the hills above the Mediterranean resort of Benidorm.
Against Nadal, Djokovic put up a better fight than he had in his error-strewn loss to Ferrer but he was unable to cope with the powerful Majorcan's superior hitting and his attempts to mix it up with dropshots largely ended in failure.
It was Nadal's 12th win in 12 Davis Cup singles rubbers since he lost his 2004 debut against Jiri Novak of the Czech Republic.
Second seeds Spain will play either Germany or Austria in the quarter-finals in July. Germany were leading their tie 2-1 after the second day's play in Garmisch-Partenkirchen.
Ferrer was due to play Tipsarevic in Sunday's remaining singles in the best-of-five tie.