Murray's exit will be a big loss for tennis: Nadal

Former champion Rafael Nadal shrugged off concerns about his fitness ahead of the Australian Open and paid tribute to fellow 'Big Four' rival Andy Murray, a day after the emotional Briton revealed plans to retire.

The 2009 winner Nadal pulled out of the Brisbane International warm-up with a thigh strain, raising fears about his campaign at Melbourne Park after his 2018 season ended early with ankle surgery and an abdominal injury.

"If I am not feeling good, I will not be here," the 17-times Grand Slam champion said at Melbourne Park on Saturday.

"I have good feelings in terms of the surgery that I have in the foot. I can say it's almost done."

In an emotional media conference on Friday, a tearful Murray revealed the pain from his troublesome right hip was proving too much to bear and said the Australian Open could be his last tournament as a professional.

Of the many banged-up players on tour, Nadal may be the most able to empathise with Murray, having spent long periods on the sidelines with serious knee problems.

"It will be a very important loss for us, for the world of tennis, for the tour, for the fans, even for the rivals that he has been part of a great rivalry between the best players for a long time, and a great competitor," Nadal said of the three-times Grand Slam champion, who he played in junior tournaments when they were barely into their teens.

"But that's life. Seems like he has not (had) a very long career because today players are playing that long.

"But he's 31. 10 years ago, if he retired at 31, we will say he had a great and very long career. That's the real thing. So all the best for him. We will miss him."

Nadal was forced to retire hurt in the fifth set of last year's quarterfinal against eventual finalist Marin Cilic, eight years after pulling out midway through his last-eight clash against Murray with a knee injury.

Doubts about the second seed's ability to withstand seven matches on hardcourts were reinforced when he retired in the US Open semifinal against Juan Martin del Potro last year.

Despite that, Nadal is leaving no stone unturned in Melbourne and brings a remodelled serve aimed at generating more pace and, hopefully, shortening points.

"You need to make yourself feel alive, you know?" he said.

"There are always things to improve ... I didn't compete with this new serve, so let's see how it works.

"I am confident it's going to work well."