Rafael Nadal has withdrawn from his Indian Wells semi-final against Roger Federer with a right knee injury.

The world number two received treatment to the knee during his gruelling quarter-final win over Russia’s Karen Khachanov on Friday.

The Spaniard looked in discomfort during the match and only had a brief practice session on Saturday.

Nadal and Federer, who have 37 Grand Slam titles between them, have not played each another since 2017.

Federer received a walkover to Sunday’s final, where he will play either Austria’s Dominic Thiem or Milos Raonic of Canada.

“I warmed up today and I felt that my knee was not good to compete at the level I needed,” he said.

Nadal completed just one hard-court tournament in 2018 – the Rogers Cup in Canada, which he won – because of his injury struggles.

He was forced to retire from his Australian Open quarter-final in January 2018 and again during the semi-finals of the US Open.

The 32-year-old reached the final of this year’s Australian Open, where he was beaten in straight sets by Novak Djokovic.

Speaking to reporters after his victory over Khachanov, Nadal said he “could not guarantee how I’m going to wake up tomorrow”.

“I love to play on hard, but probably my body doesn’t love it that much,” he added.

“My feeling is there are a lot of players that love to play on hard, true, but their bodies don’t love to play on hard, either.”