THIS is why Rafael Nadal is world no 1.
The Spanish superstar had the kitchen sink and more thrown at him by the superb 22-year-old Russian Karen Khachanov and still managed to get the job done.
Make no mistake – with the world no 26 a set up and on the brink of making it two – the reigning US Open champ looked to be in serious trouble.
With one of his dodgy knees strapped up and Khachanov’s booming serve and monster forehand working like a dream, everyone here was steeling themselves for an almighty shock.
A key moment came at 5-5 in the second set.
With the scorching temperatures replaced with overcast conditions, the rain soon came and the Arthur Ashe Stadium roof was closed.
The 12 minute break seemed to galvanise the 32 year-old from Mallorca who simply refused to go away, no matter what the Russian sent his way.
Khachanov played one of the matches of his life – as did Nadal – and it still wasn’t enough to down this remarkable , fist pumping warrior who eventually won 5-7 7-5 7-6 7-6 in a brilliantly gruelling clash which lasted over four hours.
He will now face Georgian Nikoloz Basilashvili on Sunday for a place in the last eight.
But a delighted, and relieved, Nadal said: “I prefer to play outdoors rather than under the roof but it was a tough situation and I escaped.
"I needed that second set but I am just pleased I am through and have the chance to improve."
The Russian had enjoyed some success at the Slams, reaching the third round at Paris and Wimbledon. His big hitting game is quite something.
And unfortunately for the 17 time major winner, boy was it firing here. Khachanov knew the only way to attack the Spaniard was to fight fire with fire.
The 22 year-old really took the game to Nadal – and his positive intent worked a treat.
An early break of the world no 1’s serve helped settle Russian nerves and when he broke again to make it 6-5, a packed crowd on Arthur Ashe Stadium were struggling to take it all in.
KK was brilliant but nerves began to take hold.
It took him four attempts to win the opener- Nadal was in supreme defence mode and saved three set points before a huge ace sealed the deal.
A whopping 23 winners flew past Nadal in that first set, compared to just eight coming the other way.
Nadal – who didn’t appear to be suffering – called the trainer and some strapping was applied to his right knee.
Game on. Another early break had Nadal seriously on the back foot but roared on by the pro-Spanish crowd, he managed to claw himself back in at 4-4 only for the Russian to hit back once again.
At 5-5, the momentum was still with the 22 year-old even though Nadal had just broken back. Then came the rain. It was spitting just enough for the roof to close – and soon after Khachanov’s world caved in.
Nadal came out firing after the short break and in the blink of an eye and a deafening roar from the stands, it was a set apiece and everything to play for.
The indoor conditions seemed to suit Nadal. The ferocity of his hitting increased but another razor-tight, rollercoaster set sent us into a third set tie-break.
A shoddy start on serve from the Russian allowed Nadal to ease into a 2-0 lead. Indeed his first two double faults in that set came in the breaker.
Four set points came and went for the Spanish superstar who somehow let a 6-3 lead slip. And when the fifth was finally pocketed by Nadal it took an epic 39 shot rally to finally shoot down Khachanov who was seriously announcing himself on the big stage.
The wind, however, was sucked from his sails on this occasion and Nadal managed to get an early break.
The writing was on the wall for Khachanov who was staring down the barrel at 5-4 but he managed to get himself to 0-40 on Nadal's serve before breaking for 5-5.
Incredibly, he had chances to take the set but as the longest game of the tournament so far lurched into another tie-break, the King of Spain finally held firm.
Khachanov's time, however, will surely come again.
THIS is why Rafael Nadal is world no 1.