That's long from Nadal as he's manoeuvred around the court. Tiafoe escapes for now. Deuce.

Tiafoe saves the first, as Nadal is forced into the net.

Into the net from Tiafoe!

Two break points for Nadal.

Blimey, a couple of misses from Tiafoe and Nadal soon finds himself at 0-30.

Which way will this match swing next?

That's a huge blow for Nadal, unable to make his break count, he must once again find a way through Tiafoe if he is to force a fifth set.

Laura Robson
Former British number one at Flushing Meadows

Another player struggling with the change in conditions. Nadal wouldn't usually throw in two double-faults in a game. Nadal probably struggling with the lights.

That was outrageous from Tiafoe who is screaming to himself at the change of ends here.

Tiafoe responds immediately.

A single break of serve settled each of the opening three sets, but we've already got a couple in set four!

Three successive points for Tiafoe, including that second double fault from Nadal, and the American fights back for 3-2.

Oh hello! Frances Tiafoe has a break point to get himself back on serve.

All of a sudden, Rafael Nadal is serving for a 4-1 lead in this must-win fourth set. A fifth set decider really would offer a fitting conclusion to this match.

First things first though, can he hold?

Two double faults in the space of four points from the Spaniard take Tiafoe to 30-30.

Russell Fuller
Tennis correspondent at Flushing Meadows

There is real frustration from Tiafoe about having to play when the roof is closing, who will be even more frustrated for the audible obscenity.

Huge moment!

Tiafoe saves the first break point with an ace, but Nadal hits the line with a forehand to make the breakthrough.

Tiafoe is not happy. He was thrown off his rhythm by the closing roof and now he's playing catch-up against Nadal in the fourth set.

The roof is now closed - so no more excuses.

And that could be a rather costly miss from Tiafoe, who will almost certainly have complaints if this doesn't go his way.

Two break points for Rafael Nadal!

Both players appear a little distracted by the roof as they exchange unforced errors.

And now a double fault from the American!

The roof is still closing as play commences on Arthur Ashe.

Frances Tiafoe isn't too happy with the distraction as he prepares to serve.

The rain is approaching, and the roof is closing!

Nadal comes firing back as an ace of his own helps him to 30-0. A double fault is his only blip as another ace quickly settles that game.

Lloyd Glasspool is hoping to become the third Brit to reach the men's doubles quarter-finals as he takes on Australian Open champions Nick Kyrgios and Thanasi Kokkinakis alongside his Finnish partner Harri Heliovaara on the Grandstand.

But the 11th seeds will have to go the distance with the Australian duo taking the first set 6-3.

What an escape that could prove to be for Rafael Nadal. Now, can he use that adrenaline to cause Tiafoe a few issues?

Not if he continues to serve like that! A superb ace out wide puts the American 30-15 up, before a delightful drop shot at the net leaves Nadal rooted to the spot. A comfortable hold sealed with another ace.

The third women's fourth-round match of the day is under way on Louis Armstrong between Victoria Azarenka and Karolina Pliskova, both former finalists at Flushing Meadows.

Czech Pliskova made the better start, racing to a 3-0 lead, but Belarusian Azarenka has got it back on serve at 3-2.

Big one-two punch from Nadal, and a stretched Tiafoe nets.

Nadal's box can barely watch, but their man goes down the line with a backhand beauty and then leaps to thte air in celebration.

He holds. We're up and runnng in this fourth set.

Image source, Getty Images