World number two Rafael Nadal thrashed Juan Monaco 6-1 6-1 6-2 to put Spain 1-0 up against Argentina in the best-of-five Davis Cup final in Seville.
Nadal, who crashed out of last week's World Tour Finals in the group stages, needed only two hours and 27 minutes to seal the win for the four-time winners.
The victory extended his 100% record in the competition on clay to 15-0.
Spanish world number five David Ferrer takes on number 11 Juan Martin Del Potro in Friday's second singles match.
Nadal had complained of feeling tired after his early exit in the ATP finals in London but, backed by the majority of the stadium's 28,000 fans, produced a magnificent display against world number 26 Monaco.
"I played a very solid match and I am very happy with my performance," said Nadal, whose only defeat in 20 Davis Cup singles matches on all surfaces came in February 2004 against Czech Jiri Novak.
"I was very positive before the match even if there was a lot of pressure. It's an important victory. To win by such a score against a very strong player on clay is fabulous.
"I was sad for him as he is one of my best friends."
The final is a repeat of 2008, when Spain won on a hard indoor surface in Argentina despite missing Nadal because of injury.
Argentina are seeking a first title in four attempts, having finished runners-up in 1981, 2006 and 2008, while Spain have won it on four occasions - 2000, 2004, 2008 and 2009. Serbia won the competition last year.
SPAIN 1 ARGENTINA 0
Friday's singles:
Nadal bt Monaco;
Ferrer v Del Potro
Saturday
Verdasco/Lopez v Nalbandian/Schwank
Sunday
Nadal v Del Potro
Ferrer v Monaco
