Rafael Nadal said Monday he was delighted with his remodelled serve and his fitness levels after blazing into the second round of the Australian Open.

The Spanish world number two demolished fighting Australian wildcard James Duckworth 6-4, 6-3, 7-5.

After an injury-plagued 2018, the 17-time Grand Slam champion was back to his devastating old self as he raced through in 2hr 15min.

"It was good. It is normal that beginnings are tough, but every day helps and every day makes me feel better, makes me feel more confident," said Nadal, who limped out of both the Australian and US Opens last year.

"So that's an important victory because it is the first victory since a while, and at the same time, because that gives me the chance to be on court again. And that's what I need today."

Nadal had promised to unveil a remodelled, improved serve at the first Grand Slam of the year and the new action was going smoothly until he served for the match at 5-3 in the third set only for Duckworth to break to love.

It brought a huge ovation from the home supporters and another roar as the world number 238 held for 5-5. But Nadal insisted his new serve was not to blame.

"When I get broken was not because of the serve," said the second seed who dished up just a single double fault.

"I played against a super-aggressive player. Believe me, he went on court probably doing a thing that works well for him, and it gave him some chances -- he played smart and he played well."