While all the attention has been focused elsewhere (Andy Murray’s emotional Centre Court battles, Roger Federer’s return, Novak Djokovic’s serene progress), Alexander Zverev has been quietly going about his business.

There was nothing flashy about his path to the third round, just a good solid first couple of rounds: not a set dropped and a little over three hours spent on court. And apart from a slightly messy first set tie-break once he got to Saturday’s meeting with Taylor Fritz, it was much the same. Zverev won 6-7(3), 6-4, 6-3, 7-6(4).

That fact that Fritz was here at all is something of a medical miracle. He was carted off court in a wheelchair after his second round match with Dominik Koepfer at Roland-Garros last month and was in the operating theatre of a California hospital having his right knee sliced open four days later. Now, 25 days later, he was fighting for a place in the fourth round at Wimbledon.

It happened on match point against Koepfer. Fritz jumped for a forehand and when he landed, he heard something go “pop” in his knee. He had lost the point and the match, so hobbled to the net to shake hands. But once he sat down, he soon realised that he now could not stand up again – his knee simply would not support him. That was when the wheelchair was summoned.

Fortunately, the scan results showed that the damage was not as bad as it could have been. Even so, the surgeon wanted to have a good rummage around inside the joint to be sure. If the meniscus needed repairing, Fritz would be out for six months or more. If the surgeon only needed to snip out the injured bit of cartilage and tidy things up, he was looking at a four- to six-week recovery period.

As Fritz came round from the anaesthetic, still trying to get both eyes to focus in unison, his first words were “did he snip it or repair it?”. He snipped it, he was told. And from that moment, Fritz’s every waking thought was how he was going to get himself fit and ready for Wimbledon. He had exactly 20 days to do it.

Three and a half hours of physical therapy a day may have been mind-numbingly dull but he did not care; Wimbledon was his goal and he was willing to do whatever it took to get there.

“Immediately, from then on [waking after surgery], I was just thinking, like, Wimbledon, everything I can possibly do to be here,” Fritz said. “I'm positive this is the quickest anyone has ever returned to actual professional competition from this surgery, definitely any sport that requires direction changes.”

The only noticeable after-effect is the black stocking on his right leg. This may not adhere to Wimbledon’s “almost entirely white” on-court dress code but he has been granted a special dispensation on the grounds that he is wearing it for medical reasons rather than as a fashion statement (the sole black legging look not being regarded as haute couture in either southern California or the London borough of Merton).

Other than that, Fritz looked to be unaffected by his recent injury dramas. He was running freely, flinging himself around at the net and generally looking like a bloke who was in the sort of form to get himself into the second week of a Grand Slam. All that was stopping him was Zverev.

The two men have known each other for years. Zverev is six months older and he broke out of the junior ranks two years earlier than his American pal. A little bit taller and a lot more experienced than Fritz, the German has been a part of the game’s elite for four years, collecting 15 tournament titles and reaching the US Open final last year. By contrast, Fritz, the world No.40, has just the one trophy in his collection: Eastbourne two years ago.

In essence, they are carbon copies of each other: they both have big serves, they are both aggressive baseliners and they both know what to do if it ever becomes necessary to come to the net. It is just that Zverev is that bit better at all of this than Fritz; that is why he is the world No.6. It is also why he will still be here on Monday to play Felix Auger-Aliassime for a place in the quarter-finals.

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