Carla Suarez beat Misaki Doi 6-3, 6-4, to give Spain a 1-0 lead over Japan in the Fed Cup World Group playoffs on Saturday.
Suarez settled down after a shaky start and won the first set with relative ease on the outdoor clay court at Real Club de Polo tennis club.
Spain's top-ranked player broke in the first game of the second set before jumping out to a 4-1 lead. Doi hit back to level at 4-4 but then hit her ninth double fault to drop serve, allowing Suarez to wrap up the match in the next game when the Japanese netted her return.
Spain's Silvia Soler plays Ayumi Morita in Saturday's second singles match.
Reverse singles and doubles will be played Sunday.