Rafael Nadal of Spain celebrates after defeating Karen Khachanov of Russia on Thursday. Photo: Andy Wong/AP

BEIJING – Rafael Nadal said he was braced for the “huge” serve of John Isner after Spain’s world number one bulldozed his way into the China Open quarter-finals on Thursday.

The 16-time Grand Slam champion Nadal saw off the young Russian Karen Khachanov 6-3, 6-3 to set up a clash with Isner in Beijing.

The in-form American, the sixth seed, is renowned for his booming service game and Nadal expects to come under a barrage on Friday.

Isner was impressive in blasting his way past Argentina’s Leonardo Mayer 6-0, 6-3, and Nadal said: “Tomorrow will be a tough one against Isner, he’s playing unbelievably well. 

“I saw him today, he played so aggressive, having a lot of success, hitting a lot of winners, returning very well. 

“Everybody knows that he serves huge, and it is so difficult to break him.

“But if you add that he is playing very well now from the baseline, he is one of the toughest opponents you can meet.”

Nadal, 31, the top seed and coming off the back of a third US Open title, saved two match points against Frenchman Lucas Pouille in his opener in Beijing.

But he was always in control on Beijing’s outside hard courts against Khachanov, 21, breaking him in the fourth game of the first set on the way to a routine victory.

Andrey Rublev ensured a continued Russian presence in the men’s draw as he sprang a surprise in fighting back to oust seventh seed Tomas Berdych 1-6, 6-4, 6-1.