A double fault from Popyrin and a slack backhand and it's 0-30 to Evans. The Australian gathers himself but Evans is there again at the net. Break point!

Laura Robson
Former British number one on BBC Radio 5 Live Sports Extra

You could feel that coming. It's been such a physical match and there haven't been many quick points, meaning Dan is constantly under pressure.

The one break point will do for Popyrin.

A tiring Evans suffers a dip and now the fourth set is wide open once again.

How will Evans hold up here?

The British number one hasn't played too many matches since catching Covid in July which meant he subsequently had to miss the Tokyo Olympics.

Popyrin makes a good start on Evans' serve. And is that the tiredness kicking in? Two break points.

Laura Robson
Former British number one on BBC Radio 5 Live Sports Extra

Evans is looking exhausted. He's having to work so hard at the moment for every point. It is not easy and the longer this goes, the tougher it is going to feel for him to come forward.

Much better serving from Popyrin. A hold to love, sealed with an ace.

Oh that's special. Dan Evans manages to pull off a backhanded overhead smash at a crucial moment for 30-30.

Popyrin then swings long and the British number one moves 4-2 ahead.

David Law
Commentator on BBC Radio 5 Live Sports Extra

It is just punch and counterpunch out here.

Surely not again?!

Alexei Popyrin pulls out a couple of winners for 0-30 as he aims for another quick response.

Men's second seed Daniil Medvedev has beaten Pablo Andujar in straight sets, winning 6-0 6-4 6-3, and awaits the winner between Dan Evans and Alexei Popyrin.

Meanwhile, Greek third seed Stefanos Tsitsipas looked in real trouble on Arthur Ashe at a set and a break down against Spanish 18-year-old Carlos Alcaraz, but Tsitsipas is now back level in set two.

And on Grandstand, women's fifth seed Elina Svitolina has taken the first set 6-4 against 25th seed Daria Kasatkina.

Another twist!

Popyrin's serve takes a real dip and a double fault costs him the game. Evans back in front.

Laura Robson
Former British number one on BBC Radio 5 Live Sports Extra

Evans has got two supporters in his camp who are trying to give him some energy. They are up on their feet after every point he wins.

It appears as much a mental battle as a physical one for both players right now on court 17 as both fight for the next bit of momentum.

Dan Evans sweeps away any hint of frustration at the last couple of games to bring up break point, but Popyrin volleys for deuce.

Laura Robson
Former British number one on BBC Radio 5 Live Sports Extra

This is where you wonder how much the lack of matches and training has affected Dan over the last couple of weeks. Having Covid-19 and having to take time off before the hot and humid hard-court swing is not ideal preparation at all. He is such a good competitior and he never, ever gives in.

And just like that, Popyrin is back level in the fourth set.

After Evans passed up two break points, he only manages the one point on serve and the Australian is on the up.

Laura Robson
Former British number one on BBC Radio 5 Live Sports Extra

It is so draining to be that pumped up. You're always going to have a bit of a dip after that.

David Law
Commentator on BBC Radio 5 Live Sports Extra

Dan Evans looks a bit tired, to me - but then he always looks tired.

Popyrin rescues the situation with a couple of backhand winners of his own, with Evans unable to take advantage of a second serve on his second break point.

There's to be no double break, as Popyrin gets himself on the board.

Laura Robson
Former British number one on BBC Radio 5 Live Sports Extra

The serve has really left Popyrin in the last couple of game. He's throwing in double faults at really bad moments.

Evans is really delivering on the backhand. Another gets him ahead on the Popyrin serve and a double fault by the Australian makes it 15-30.

A miss! Two break points to Evans...