Nadal, who captured 22 Grand Slam titles in a glittering career, will make his final bow in the team event being staged in Malaga starting Tuesday.
Spain will face the Netherlands in their opening match in what is likely to be a momentous occasion.
“It’s probably the most special tournament I’ll play in my career, because of what’s happening, because of the circumstances,” Alcaraz was quoted by the ATP website after arriving in Spain following his ATP Finals exit.
“The Davis Cup has always been a tournament that I’d love to win one day, I’m passionate about representing Spain.
“Having Rafa by my side, knowing it’s his last tournament, will make it much more special.”
The 21-year-old Alcaraz, who already owns four Grand Slam titles, played with Nadal at this year’s Paris Olympics, the pair losing in the quarter-finals.
“I’ll try to contribute and help the team any way I can – for me, for Spain and especially for Rafa,” Alcaraz said.
“No player deserves more to finish the incredible career he had with a title, and I know how special the Davis Cup is for him. It will be a difficult challenge but winning it for Rafa is a huge motivation.”
Spain have won the Davis Cup six times, the last occasion in 2019 when Nadal inspired the hosts to the trophy in Madrid.
“Rafa’s farewell is much more important, at least for me,” Alcaraz said. “The Davis Cup is every year. Rafa’s farewell, saying goodbye to a legend of the sport, unfortunately only happens once. Personally I’m very excited to be by Rafa’s side for his farewell.
“And the fact that it’s in the Davis, which is a very important tournament for him, virtually where he started his career with that victory against (Andy) Roddick (in 2004).
“It will be an incredible event because of the occasion and hopefully it will end with the title.”
Eight nations are contesting the Davis Cup Final Eight with action taking place in Malaga between Nov. 19 and Nov. 24.