"Honestly, I'm not too alarmed or too negative about what happened. There was a real chance to lose these kinds of matches," said Nadal after falling to Alex de Minaur in Sydney.
"There is room to improve. I really believe I can do it."
Nadal dropped six consecutive games after leading a set and 1-0 against de Minaur as the Australian turned the match around for a 3-6, 6-1, 7-5 upset in Sydney.
Nadal also lost to Cameron Norrie in his country's first tie at the mixed-teams event as Spain were beaten by Great Britain at the weekend.
With his singles run over at the inaugural edition of the competition, being played in three cities, 22-time Grand Slam winner Nadal is keen to get to Melbourne and train for his Open title defence starting in a fortnight.
"I have two weeks before the start," Nadal said. "I can't say the situation is ideal, but I can't say that it's very negative.
"For moments I was playing well, two matches are going to help. I arrived needing a little bit more time."
The veteran said he was outplayed by world number 24 De Minaur.
"He played better in the important moments. I had my chances but I made important mistakes at those moments that I can't do if I want to win."
