Russell Fuller
BBC tennis correspondent on BBC Radio 5 Live Sports Extra

This could be a gruelling match.

Now that's a first serve!

Down the T goes Nadal, and Medvedev's return drifts way, way long.

Nadal can't buy a first serve at the minute, and an easy, flat-footed miss of a forehand gives Medvedev another break point.

Andrew Castle
BBC Sport tennis commentator at the O2 Arena

It takes Medvedev just three steps to get across the baseline. He is like a very quick giraffe.

Saved!

A long rally and it's Medvedev who blinks first, his backhand drifting over the baseline.

Back to deuce we go.

Trouble!

Nadal goes cross-court with a trademark forehand, misses, and Medvedev has an early break point...

Nadal slices and dices his way through a rally but it's Medvedev who comes out on top, latching on to a short return, but Nadal makes up for it with a supreme serve out wide that not even Stretch Armstrong could return.

Nadal's within touching distance of a hold but another outrageous, flat forehand from Medvedev bursts through Nadal's racquet, and we're at deuce.

Russell Fuller
BBC tennis correspondent

There has been some spectacular shot-making already.

Ooft. Daniil Medvedev absolutely nails a pair of flat backhands, sending the ball flying cross-court and beyond a rooted Rafa Nadal.

Nadal spears a winner of his own down the line, but an error on the backhand hurries Medvedev along to a hold.

Andrew Castle
BBC Sport tennis commentator at the O2 Arena

There looks to be a clarity about Nadal's game tonight.

Shot! Nadal dances forward and sends a glorious, whippy forehand winner spinning onto the lines. Lovely.

It's game point to Nadal, and he takes it as Medvedev nets a backhand.

Dominic Thiem is watching on from the stands, presumably scoping out tomorrow's opponent.

Rafa takes advantage of Medvedev being stood so far behind the baseline by serve and volleying his way onto the board, before the Spaniard slides another backhand long for 30-30.

The first point of the match goes Daniil Medvedev's way as Rafa Nadal twirls a backhand just over the baseline.

Ready?

Play.

* denotes next server

Andrew Castle
BBC Sport tennis commentator at the O2 Arena

I think we're going to see the flat ball from Medvedev - that will give Nadal some trouble. He's a quick player. If Medvedev serves well he's going to give Nadal kittens here. If he starts hitting his spots, especially the wide ones on the deuce side of the court, then he is the man to beat.

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The coin toss goes Daniil Medvedev's way, and he opts to receive first up.

And here's what these two players make of one another...

Daniil Medvedev enjoyed a breakthrough 2019 season, but he didn't fare so well in London, going 0-3 in last year's tournament.

However this year, he is the only semi-finalist who went through the group stages unbeaten.

That included a fine 6-3 6-3 win over no less an opponent than the world number one, Novak Djokovic.

Image source, Getty Images

Rafa Nadal is unbeaten in three meetings with Daniil Medvedev, but the last two have been close encounters.

Nadal prevailed in a mammoth five-set US Open final last year, where Medvedev almost overturned a two-set deficit.

In the group stages of this event in 2019, Medvedev held a 5-1 lead in the deciding tie-break, but Nadal gritted his way through to victory.

Image source, Getty Images