By winning the French and US Open titles last year, Rafael Nadal showed that talk of his demise had been exaggerated.

Still, he faces a battle to repeat those feats without his uncle and lifelong coach Toni, while also fighting familiar injury troubles.

Nadal returns to the Australian Open, where he lost a thrilling five-set final to perennial rival Roger Federer in 2017, after overcoming chronic knee problems just in time.

He's hoping to continue last year's progress under new coach Carlos Moya.

Former world No 1 Moya will lead Nadal's team, after spending last season with Rafa and Toni preparing for the latter's retirement, having helped Nadal roar back to life after a barren three-year spell without a Grand Slam trophy.

Moya can take some credit for the vast improvement in Nadal's second serve, which helped the Spaniard win a 10th French Open title without dropping a set and saw him blow away Kevin Anderson to lift the final major of the year in New York.

"I increased my serve by several kilometers per hour and I think I did better overall with my second than first, and I can say I won some points almost for free as a result," Nadal said in a recent interview with Spanish daily AS.

"We'll have to keep working on that because in my career there are two vital things－the serve and the return－where I start the point and where I have to attack so I don't have to run more than I need to.

"It's a new era and will be like adapting to a different routine. Moya has come with new ideas and new methods of working that have worked well, and we are excited."

Nadal, 31, became the oldest player to end the year as world No 1, although the stresses and strain on his body finally took their toll when he had to pull out of the ATP World Tour Finals in November after losing his opening-round match.

That was his last competitive action as he missed warm-up events in Abu Dhabi and Brisbane and only returned for the Kooyong Classic exhibition tournament on Jan 9, in which he lost in straight sets to Richard Gasquet.

Nadal was naturally rusty after his extended break but looked free from his notorious knee problems and is not alone heading to the Australian Open after injury troubles.

Andy Murray has had to extend his six-month absence by having hip surgery, while Novak Djokovic and Stan Wawrinka have not played competitively since Wimbledon in July although the pair, unlike the Briton, will be at Melbourne Park.

Nadal's biggest challenge, and that of compatriot Moya, will be to beat tournament favorite and world No 2 Federer after losing all his four matches against the Swiss last season.

Federer took his Grand Slam tally to 19 after extended rest breaks and Nadal, who enters his 18th season on the ATP tour, has also benefitted from carefully picking tournaments to preserve his fitness.

"My schedule in 2017 was the correct one, only playing the tournaments that were practically obligatory and the occasional warm-up event," he told AS. "My plan for 2018 is similar and my aim is to miss out a few more events, but it will depend on results."