Top-ranked Rafael Nadal beat Olivier Rochus 6-4, 6-2 to extend Spain's domination over Belgium to 4-0, one day after Spain qualified for the quarterfinals of the Davis Cup.
However, Feliciano Lopez lost the second dead rubber 7-6, 6-7, 6-7 to Steve Darcis preventing a clean sweep for Spain.
Nadal's outing on Sunday gave him more practice ahead of the next week's BNP Paribas Open in Indian Wells when he will play his first ATP event since injuring his left thigh during the quarterfinals of the Australian Open.
Nadal had already won a singles match for Spain on Friday, a straight-set win over Ruben Bemelmans. Both Rochus and Bemelmans are ranked outside the top 100.
Spain will play away and face the United States on July 8-10.