It's harsh and there is still a long way to go but it's those lapses that cost Taylor Fritz in these big matches.

Zverev stands tall and imperious to take this next game, winning a rally that lasts more than 20 shots.

It means we're back level but it's clear who is looking the stronger now.

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra and BBC Sounds

That was a horrid game for Fritz. I did not see that coming and thought he was taking advantage of a below-par Zverev at the other end.

Image source, Getty Images

Fritz goes into the net. The American's racquet thuds into the court.

Back on serve.

What was I saying? Alexander Zverev unleashes on the forehand and here are two break points to get back on serve.

David Law
Commentator on BBC Radio 5 Sports Extra and BBC Sounds

Zverev is a master of the five-set format. He outlasts so many players and is a real fighter.

Alexander Zverev still looks fit. He looks like he's hardly broken sweat and needs to tell himself this can still be turned around.

Taylor Fritz is motoring. Zverev, in contrast, has to drag himself to his chair.

Isn't it funny how things can change?

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra and BBC Sounds

It's amazing how much Zverev's forehand fluctuates and loses it smoothness during matches when he's under pressure.

It must be so frustrating when he's worked so hard to get that breakthrough in the second set and now a little loss of concentration early in this third set could really cost him.

Got it!

Another error from fourth seed Zverev gives Taylor Fritz his first break of the match.

Now it's Taylor Fritz's turn to apply the pressure.

The crowd lift themselves in anticipation as a backhand error gives the American two break points.

Not this time for Alexander Zverev. That was a really dangerous moment for Taylor Fritz but he found a couple of clean strikes.

Remember the American has lost all four of his previous Grand Slam quarter-finals.

Right away we have 'a moment'.

Taylor Fritz is nearly blown over backwards by a Zverev return.

Break point for the German at the start of this third set...

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra and BBC Sounds

Just amazing, I think Alexander Zverev deserved that set.

This match was never going to be straightforward and it always felt like it was going to go the distance so who knows what is going to happen in the next couple of sets.

We're in for a real fight here.

Image source, Getty Images

And on such small margins are these matches won!

From nowhere Alexander Zverev has snatched this set.

After so much good work early on, Taylor Fritz has seen his advantage wiped out.

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra and BBC Sounds

Alexander Zverev is making his move forward and I do wonder whether he has to start doing that more, adding pressure.

He has got a good wingspan and he should be introducing that play a little bit more.

It's amazing that he was about to smash his racquet because he hasn't had a breakthrough and then everything changes in the blink of an eye and he is going to serve for the second set.

Long goes Taylor Fritz via the frame! Alexander Zverev roars. He's got his break.

Alexander Zverev shapes to obliterate his racquet after missing a backhand. Fortunately for the racquet, court and his bank balance he aborts.

He's sniffing an opening. Here's his first break point of the match.

Zverev survives with another serve in excess of 130mph.

Fritz is getting his racquet on so many of these. It's rarely easy for the German.

A 133mph second serve from Alexander Zverev! Someone check the record books. It's the fastest serve - first or second - he has hit in this set.

A sign of confidence or desperation? The next is a double fault.

Deuce...

Image source, Getty Images

Taylor Fritz accepts an invitation to hit a running winner of his own. It wasn't as good as Zverev's but it means he has 30-30 on the German's serve.

The crowd senses something...