A wonderful deep slice from Novak Djokovic wipes out Auger-Aliassime's advantage and the Canadian then dumps a return into the net to trail 40-30.

One big serve later and the seven-time champ is on the board.

Naomi Osaka perhaps glimpses an opportunity as she arrows a forehand winner beyond Karolina Muchova but the Czech quickly snuffs it out.

Two massive serves, the second an ace, take the 10th seed to another hold.

Pat Cash
Former Wimbledon champion on BBC Radio 5 Live

This standard of tennis here we've seen in this match, it's extraordinary. It's the highest I've seen for a long time.

Novak Djokovic arches his shoulders to take on a high forehand winner to begin this quarter-final on Centre Court.

But follows it up with a double fault to a fair few oohs from the crowd.

And those oohs turn into aahs for a fine Felix Auger-Aliassime backhand winner. 15-30...

This record is going to take some beating - 106 Wimbledon men's singles match wins, only 13 losses.

I mean, Pete Sampras was dominant at Wimbledon for a period.

And yet he's a dot in the distance compared to Novak Djokovic and Roger Federer.

The only question left is how high can the Serb set the mark to beat? 110? More? It doesn't feel like he's retiring this year...

Martina Navratilova
Nine-time Wimbledon singles champion on BBC Two

Karolina Muchova had a couple of break points right at the beginning of this set, but both players have held for an extensive period now. The last four service games have been very authoritative.

A bit of pressure at 15-30? Not if you're Naomi Osaka.

She digs in once more and then hammers down another ace - right down the T - to hold.

Image source, Getty Images

To be still competing at the highest level of men's professional tennis at the age of 39 (he turns 40 next May), is a testament to Novak Djokovic's amazing endurance and brilliance.

To illustrate that further, only two players - Federer (2) and Ken Rosewall (3) - have ever reached multiple Wimbledon semis after turning 35. Djokovic is aiming for his FIFTH...

Only Rosewall (39 years 246 days) has been an older Wimbledon semi-finalist - and with respect, the fitness levels required at the top end of the game are surely a bit higher than they were in the 1970s.

He's pretty much facing players a decade or more younger than him every time he steps on the court nowadays - but Djokovic may well be the most formidable opponent tennis's version of Father Time has ever encountered.

Harry Poole
BBC Sport at Wimbledon

Almost an hour and a half in and no sign of either player beginning to wilt in the 30-degree heat.

It continues to be a classy match, and hopefully one which is going to be decided by moments of real quality.

"High-quality tennis," is the assessment from Martina Navratilova on commentary - and coming from a nine-time Wimbledon champion, that means something!

Superb hitting from both players but it's Karolina Muchova shining in this game.

An excellent lob and then a second-serve ace to close out a hold to love.

Image source, Getty Images

Novak Djokovic has been taken to four sets in three of his four matches at Wimbledon so far this year.

Indeed, he displayed visible signs of frustration during his fourth-round victory over qualifier Roman Safiullin.

Opponent Felix Auger-Aliassime cruised through his opening three matches in straight sets. But he was taken all the way in round four by Alejandro Davidovich Fokina in a five-set thriller.

Whomever won that match was always going to test both Djokovic and the spelling and typing fingers of a live text tennis writer... (can we just use FAA for short?!)

Emily Salley
BBC Sport at Wimbledon

The big news is that Novak Djokovic has ditched his fancy blazer and opted for a sports jacket today.

That sounds like he's a rebellious school kid.

Kat Downes
Commentator on BBC Two

Naomi Osaka didn't hold back with that second serve! It was right into the corner of the service box.

A fight is well and truly on for this second set, which is still on serve.

Here comes the medic to help Karolina Muchova out with something that has popped into her eye. There is a lot of dust out there because it has been so hot.

Image source, Getty Images

It's fair to say big things have long been expected of Canada's 6ft 4in Felix Auger-Aliassime.

And there are signs he is beginning to live up to those lofty expectations after rising to a career-high number four in the world rankings.

He is yet, however, to reach a Grand Slam final - two semi-final appearances at the US Open his best runs in the majors.

Auger-Aliassime has a 3-8 win-loss record against fellow top 10 players in Slams - although it's 3-2 on grass. But he faces a big challenge to improve that further today, of course.

Naomi Osaka takes a deep breath to quell her anger after sending another aggressive forehand long.

The 14th seed keeps that same composure, sends down her fifth ace, and goes on to hold to 30.

Still on serve but the medic is out to see Karolina Muchova at the change of ends. Hopefully it is nothing serious because the Czech has played so well here.

Image source, Getty Images

The numbers, records and statistics relating to Novak Djokovic's career and success are so vast and plentiful they almost lose meaning.

Victory today, for example, would ensure a record-extending 55th Grand Slam semi-final appearance for the Serb - and his 15th at Wimbledon.

If he wins today, it would be an eighth successive SW19 semi - and he'd take sole ownership of that record, currently sharing it with old friend/foe Roger Federer (this after taking another record off the Swiss yesterday - most Wimbledon match wins).

And, of course, he's after the BIG ONE - an outright record 25th Slam singles title (level on 24 with Margaret Court).

Calm and composed, even in the heat at Wimbledon, Karolina Muchova gets another forehand right out of the screws for a winner.

That secures another stress-free hold and keeps it on serve in the second set.

Right, you know what's up next on Centre, don't you? Of course you do.

Youth might be on his side - and in fairness, so is his world ranking - but one look at two of the stats above will show what a task Felix Auger-Aliassime faces today.

His run to the quarter-finals has matched his previous best ever Wimbledon performance - but now seven-time SW19 champion Novak Djokovic stands in his way.

A man whose career trophy haul runs into triple figures. Time, of course, is his main adversary in attempting to add to that tally. But he'll see the lush grass courts of London as one of his better chances to do so.

World number three Alexander Zverev, speaking on Centre Court after beating Jiri Lehecka to reach his first-ever Wimbledon quarter-final:

"Who would've thought it would've taken me only 12 years to get here? I'm incredibly happy and relieved to achieve that, but of course I want to play three more matches here.

"It was a fantastic match that lasted two days, and of course it is never easy to come back on the following day. I thought Jiri [Lehecka] played amazingly today, so credit to him for keeping the fight up and making it very difficult for me.

"For me, it was a bit difficult [to get going again today]. I lost the first three games and I gave away the third set, but again he came out playing incredible tennis and he came out swinging so credit to him. He did a fantastic job in that aspect. I'm just happy to be through in four sets and I'm glad I didn't have to play another set.

"I think it is more difficult mentally than physically not having time to breathe, realise what's happening and prepare for the next match. Playing back-to-back days, especially best of five sets, isn't easy but I'm very happy to be playing tomorrow. That's the most important thing. I hope I'll be back on this wonderful court and playing my best tennis again."

On what sort of match he expects against Taylor Fritz: "Probably not a very entertaining one! We both serve 140mph so I would expect there won't be many rallies. At the end of the day, this is grass court tennis so everything very fast. I'm going to do everything I can to be playing my best tennis tomorrow."

Image source, Getty Images

It was far from easy but Naomi Osaka comes through to hold.

Karolina Muchova is a set up and looks the stronger of the two so far. But these things can change very quickly, which is why she'll be disappointed not to have converted that break opportunity.