Rafael Nadal sent Karen Khachanov warning at Indian Wells, Roger Federer semi-final claim

That’s according to former British ladies’ No 1 and Amazon Prime tennis pundit Sam Smith.

Nadal takes on Khachanov in the last eight in the Californian seeks to set up a clash with long-time rival Roger Federer.

The pair have already watched world No 1 Novak Djokovic crash out in a surprise defeat to Philipp Kohlschreiber and if they meet in the semis, the winner will be heavily fancied to go on and win the tournament.

But Smith insists neither Nadal or Federer will be thinking so far ahead, despite the possibility of a 39th career showdown.

And nor they should according to Smith, because she thinks Russia’s Khachanov – who won the Paris Masters last November – could offer a real threat to Nadal.

Speaking on Amazon Prime’s Indian Wells coverage, she said: “I’m quite concerned about Khachanov. 

“I think that for me is going to be the more interesting of the quarter finals.”

Asked whether Nadal and Federer will know they could meet in the semis, Smith added: “Those two – they know everything! It’s extraordinary, it’s like they’ve both got eight brains. 

“They are across all sorts of things you wouldn’t almost believe. But one thing they don’t do is get ahead of themselves. 

“Rafa would underestimate his grandmother going on to court. He needs to be very worried about Khachanov. 

“Take away forehands and backhands, I look a lot at how a player carries him or herself on court and he [Khachanov] has got such a confident walk. 

“I don’t think he has any doubts that when the big moments come he’ll be able to take out the top players.” 

Fellow panellist and commentator Nick Lester added: “I think Khachanov has got the game to really trouble Nadal, I really do. 

“He can trouble you. He can push Nadal off the baseline and not many guys are able to do that.”

Nadal owns a 5-0 record against Khachanov until now, though the 22-year-old led by a set when they last met in the US Open last year.

The Spaniard, however, dug deep and roared back to win 5-7, 7-5, 7-6, 7-6 in a thrilling contest.

The 17-time Grand Slam champion is looking for what would be a fourth triumph in the Californian desert, while Federer is aiming for his sixth success to become the most successful player in Indian Wells history.