Rafael Nadal cast doubt on his fitness for the Australian Open by pulling out of the Brisbane International ahead of his first match.

The Spaniard opted not to play his second match at an exhibition event in Abu Dhabi last week after tweaking his thigh and is worried about the risk of exacerbating the problem.

Speaking at a press conference, he said: "I did an MRI and it shows a small strain on my left thigh. I tried to play, I wanted to play, but recommendations from the doctors (were otherwise).

"I feel better than I did four days ago. It's a risk to damage my body for one month if I play here."

It continues a trend for Nadal, who withdrew or retired mid-match during all but one of his hard-court tournaments last season.

His final match of 2018 turned out to be the US Open semi-final against Juan Martin Del Potro, where he pulled the plug at the end of the second set because of pain in his troublesome knees.

After recovering from that, an abdominal injury sidelined him for the rest of the season and he began his pre-season preparations late after opting to have ankle surgery to clear up a persistent niggle.

This latest issue is a dispiriting blow for the world number two but he will hope sitting out this week will enable him to be fully recovered for the year's first grand slam, which starts on January 14.

Japanese lucky loser Taro Daniel takes Nadal's place and faces Jo-Wilfried Tsonga in the second round.