"For us, it was very important after two years being away from the World Group," said the 14-times grand slam singles champion.
"It's important for us to come back to where we think we have to be."
The tournament's dominant power of the modern era, Spain won five titles from 2000-11 before decline set in following their tight loss in the 2012 championship decider to Czech Republic.
With Nadal battling injury and his top team mates' commitment wavering, Spain were turfed out of the World Group in 2014 after being upset by lowly Brazil in a playoff, sparking then-captain Carlos Moya's resignation.
Moya's replacement Gala Leon was sacked within a year after a players' revolt and Spanish tennis was further embarrassed as the team crashed out to an understrength Russia in the Europe/Africa Zone Group I last year under new captain Conchita Martinez.
Former Wimbledon champion Martinez, who also captains the women's Fed Cup team, has been at pains to repair relations with her players and managed to bring a strong team to India to get the job done.
Former Davis Cup power Australia also has ambitions of returning to its glory days and will keep their place in the World Group after defeating Slovakia 3-0 in Sydney.
Led by talented but tempestuous 21-year-old Nick Kyrgios, the 28-times champions have a player to build a team around and captain Lleyton Hewitt said he expected big things in 2017.
"We expect that we can go deep," said the two-time grand slam champion and former Davis Cup winner.
"It's been quite a while now since we've had an opportunity to play in a final and I know from experience I'd love these boys to have that experience of going out there and playing for Australia."
Belgium, Canada and Japan also booked their places in the World Group next year.
Champions England, trailing 2-1, continue their Davis Cup semi-final against Argentina later on Sunday, with Croatia aiming to wrap up the other semi-final against France.
(This corrected version of the story fixes Lopez's first name in second paragraph).
(Reporting by Ian Ransom in Melbourne; Editing by Sudipto Ganguly)
