Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra 2 and BBC Sounds

I am kind of looking at whether Jakub Mensik is talking to himself. The dialogue would be: 'I am not serving great, but I am still in the first set.' It was a much cleaner game on serve to hold from Mensik.

Another shake of the head from Alexander Zverev as he slides into a drop shot on the second bounce. It's an effective weapon from Jakub Mensik. 30-15.

He completes the hold to 30 after getting a second serve to rise into Zverev's body, cramping him for room.

That's his first service game which hasn't gone to deuce.

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Another trouble-free hold for Alexander Zverev, this time to 15. He's only dropped one point in his past two service games.

One thing he hasn't done yet is hit an ace.

David Law
Commentator on BBC Radio 5 Sports Extra 2

When you watch Jakub Mensik play it is hard to believe that he is ranked 27th in the world.

Naomi Broady
Former British player on BBC Radio 5 Sports Extra 2

Players seem to be unafraid. I think they just really embrace it and feel they should be out there. They stride through the match like it is nothing. They are such big-match players in the Grand Slams.

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Three service games taken to deuce for Jakub Mensik. Three holds.

But Alexander Zverev is knocking on the door.

Jakub Mensik gets a taste of his own medicine as Alexander Zverev leaves him stranded on the baseline with a backhand drop shot.

A double fault for 0-30 invites more pressure on his serve.

He levels the game with an ace down the T and a well-disguised short forehand but has mixed fortunes after getting into consecutive baseline exchanges with the German.

Off we go to deuce again.

Naomi Broady
Former British player on BBC Radio 5 Sports Extra 2

Alexander Zverev is number one on the ATP leaderboard for first-serve percentage, which is pretty incredible after all the yips he had all those years ago.

A routine hold for Alexander Zverev despite only landing two first serves.

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Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra 2 and BBC Sounds

To me, Jakub Mensik has to be able to do that volley now and then, but at least once a game.

Watching Alexander Zverev sprint to that drop shot, he arrived off-balance. That is why Mensik has to continually probe that drop shot.

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Another hold for Jakub Mensik. He's been taken to deuce in each of his opening two service games but is yet to face a break point.

Both players are still feeling their way into this semi-final.

Jakub Mensik is really enjoying his drop shots. His latest effort has lots of backhand slice and although Alexander Zverev makes up the ground on the slide, his reply doesn't clear the net.

However, he nets a tame forehand to surrender advantage.

Jakub Mensik recovers from 0-30 down to lead 40-30, serving and volleying off the back of a wide serve to set up game point, but once again, we're going to deuce.

Naomi Broady
Former British player on BBC Radio 5 Sports Extra 2

It's unbelievable the athleticism of these guys. They are moving like they are 5ft10.

Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra 2 and BBC Sounds

Alexander Zverev has the ability up at the net, but we have not seen it often enough. He is stepping onto the doubles court, and that reaction making the volley you will see on a doubles court. He is starting to make these subtle changes, which are starting to pay off.

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Alexander Zverev hunts down Jakub Mensik's drop shot, pummels his return deep into the corner on the Czech's backhand, and is in position to stroll towards his volley winner.

A steady hold for the German.

Jakub Mensik is forced off court by an inside-out forehand but races back to the opposite side to unleash a backhand pass with Alexander Zverev at the net: 40-30.

Zverev shakes his head after sending a groundstroke long. Another game going to deuce after the server led 40-15.

Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra 2 and BBC Sounds

I have noted how many times Jakub Mensik has come to the net throughout the tournament. I think it is part of his weapons and strengths. You have got to put it into play no matter who your opponent is.

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Jakub Mensik is showing plenty of enthusiasm for coming into the net, completing the hold with a serve and volley.

It's Alexander Zverev who gets the first point on the board, Jakub Mensik netting a backhand.

The young Czech recovers to lead 40-15, including a teasing drop shot for 30-15, but is pegged back to deuce after a couple of unforced errors.