New Zealand won the Rugby Championship last weekend. Again. They did so with one-third of their matches still to be played. Again. The last time the All Blacks failed to win the title in a non-World Cup year was 2009 when South Africa were on the high of a successful Lions series.

Since then, and excluding 2011 and 2015 when New Zealand mixed and matched with the World Cup in mind, they have lost one match in six campaigns, to a long-range penalty by Pat Lambie one minute from the end against South Africa in 2014.

The Springboks stand between New Zealand and a fifth grand slam this decade at Newlands on Saturday, the All Blacks’ first visit to Cape Town since 2008. They may have to cross a picket line to get into the ground with a union set to organise a protest against South Africa’s Test matches being covered live on subscription television rather than free-to-air.

Meetings between New Zealand and South Africa used to be the highlight of the rugby calendar; hard fought, unyielding and close. The Springboks won six consecutive Tests in the series between 1937-49. At the end of the amateur era in 1995, South Africa had won 21 matches against the All Blacks, lost 18 and drawn three.

All that remains the same now is the number of draws with New Zealand leading the series 56-35. It was not until 1965 that the All Blacks beat their rivals by a double-figure margin but last month they won 57-0 in Albany and scored the same number of points in Durban a year ago while conceding 15.

The only surprise when the South Africa coach, Allister Coetzee, said his team would be “living in a fool’s paradise” if they thought they would win on Saturday was that he made it publicly. Perhaps he was, like one of his predecessors Peter de Villiers, trying to get inside the heads of his opponents but more likely, given that most experienced South Africa internationals are playing in Europe, he was giving his relatively raw side a licence to get stuck in unencumbered by even a few grams of pressure.

South Africa’s starting lineup against Australia last weekend had a collective 355 caps, 207 of which were on the heads of three players, Tendai Mtawarira, Eben Etzebeth and the hastily summoned Francois Louw. That number was exceeded on the same day by Montpellier and Stade Français whose six Springboks shared 395 caps.

There are 90 capped players from the four countries in the Rugby Championship registered to play in the two European competitions this season: 32 are from South Africa and include the current Springboks centre Jan Serfontein who is joining the collection of his countrymen at Montpellier in a few weeks; 27 from New Zealand; 20 from Australia; and 11 from Argentina.

New Zealand and Argentina do not consider for selection any player who is playing elsewhere and Australia have a 60-cap rule. South Africa have no exclusions but have a stated preference for players who are based in the country. The Worcester scrum-half Francois Hougaard was the only player who faced the All Blacks last month who was called up from abroad, and he was joined in the squad after that drubbing by Louw.

It should be no surprise that the Rugby Championship is declining as a tournament, most notable now for the ability of New Zealand to absorb the loss of so many players. If there was an exodus from north to south it would have an even bigger impact on the Six Nations because there is not a team in Europe comparable to the All Blacks, hard though England are striving to catch up with the World Cup holders.

Professionalism has highlighted two areas that are threatening the primacy of international rugby. Playing standards, generally, are set in the south – there are even more New Zealand coaches in Europe than there are players but the money is concentrated in the north. No matter how much Charles Piutau covets wearing the black jersey, the prospect of earning nearly £2m at Bristol from next season – even if the club fails to gain promotion from the Championship – makes dreams fade into reality.

As Stephen Brown, the recently appointed chief executive of the Rugby Football Union, acknowledged this month European countries need South Africa and Australia – who are left again to fight for a distant second place to New Zealand – to remain attractive to the paying public every November.

While England would probably sell out at Twickenham against Papua New Guinea’s A side, such is the pull they have sustained since the Clive Woodward era, it is different for Wales, Scotland and Ireland. Wales face South Africa in Cardiff in December in a Test outside the international window, a match the Welsh Rugby Union needs to fund its four regions, but how high can ticket prices be set for a match against a team in decline which lacks any box-office names?

South Africa winning on Saturday would help. In the last two years, New Zealand have defeated Australia heavily one week and found it harder going the next, but it almost seems that South Africa are for once giving themselves the advantage by playing at sea level, saving their lungs.

The Six Nations has not in recent years been renowned for the quality of rugby it serves up, although there have been moments. It is draped in history and passionately followed but the average attendance in this year’s Rugby Championship is under 30,000 with three of the 10 gates below 20,000. As players go, so standards fall, and the All Blacks will be harder pushed on their tour of Europe next month, even without meeting England and Ireland, than they have been since the Lions returned home. Test rugby needs a health check. Problems cannot be cured in isolation.

• This is an extract taken from the Breakdown, the Guardian’s weekly rugby union email. To subscribe, just visit this page and follow the instructions.