One by one they stop at the St. Regis Hotel in Riyadh.

Jannik Sinner, Carlos Alcaraz, Rafael Nadal, Daniil Medvedev and Holger Rune have arrived – only Novak Djokovic has yet to join the biggest stars in men's tennis by accepting flowers, drinking tea and chatting with Turki Alalshikh, chairman of the Saudi General Entertainment Authority -Arabia, maintains (GEA).

They are the show and they are here in the Saudi capital for another one. One of the richest shows in tennis history, a $15 million (£11.9 million) bonanza that the kingdom calls the “Six Kings Slam”. The winner takes home $6 million. Just being there brings in over $1 million.

Two weeks later, the WTA Tour hosts its season-ending finale, another $15 million payday for the year's top eight women's singles players and top women's doubles teams. The ATP Next Gen Finals, an event featuring the top eight men in the under-21 rankings, will be held in December in Jeddah, Saudi Arabia's second-largest city and commercial hub.

For the rest of the season, this Gulf state will assume the role of the heart of the tennis universe, as unlikely as that may seem for a country where people hardly practice the sport and important tournaments have never taken place. After years of pressure, everything appears to be in place for Saudi Arabia's multi-billion dollar move to become a major force in tennis – with a big catch.

After months of back-and-forth negotiations and due diligence between the kingdom and the entities that control the sport of tennis, the proposal for a major mixed 1000-level tournament (one tier below the four Grand Slams) in Saudi -Arabia January or February is still at least three seasons away, a casual gesture given the seismic shift that is only slightly more concrete than a year ago when it roiled the sport.

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The biggest advantage of Saudi Arabia's three-team foray into tennis remains just an idea, as there is uncertainty on both sides about the tournament's size, schedule and funding. There is no guarantee that it will come to pass. No decision has been made yet on who will attend or how much it will cost, according to people briefed on the discussions who spoke on condition of anonymity because they are not authorized to speak publicly.

The proposal has become such a question mark that it played little role in meetings between the ATP and WTA tours and the four tennis associations that control the Grand Slams at this year's US Open. Months of discussions between Saudi sports leaders and ATP executives – closely watched by WTA executives – have failed to produce agreement on even the most basic tenets of a tennis tournament:

• When should such an event take place?
• Will only the top 56 men take part or will there be a larger draw?
• Will it be a mixed event, as the Saudis would prefer, putting the tournament on par with other 1000-level tournaments such as Indian Wells, Madrid and Rome – some of the most prestigious of their kind?

Mounting complaints from players about the length and logistics of the sport's current schedule have further complicated discussions. Tour officials know this is not the time to announce a new mandatory tournament, especially one that could shorten an offseason that most agree is already too short.

Additionally, the answers to the above questions will have a significant impact on how much money the event could raise and how much Saudi Arabia's Public Investment Fund (PIF) wants to invest in the company through its sports arm SURJ Sports Investment. The big promises from 12 months ago have been fulfilled.

The PIF has major sponsorship deals with the ATP and WTA tours. (PIF/Getty Images)

“It wasn’t at the forefront of discussions because it doesn’t make sense,” said one of those involved in the Grand Slam meetings at the US Open. “We assume that this is not a cause for concern.”

With their coup de grace still up in the air, the Saudis have opted for a more measured approach, people familiar with their plans say – an approach that gives the next month or two of tennis an air of makeshift. Saudi officials refuse to talk about their big plans for tennis because they don't know where those plans might lead.

They'll test the waters with their biggest and most expensive show – the Six Kings Slam offers one of the biggest cash prizes in tennis history.

Then the women will arrive for their tour finals so the country can gauge interest and determine how hard the kingdom should push for investment in tennis over the next decade. The Saudi contract with the WTA runs until 2026 and allows all parties to explore each other's strengths and weaknesses.

How many people will take part? Will the infrastructure hold up? Will the media impressions come true? The plan is to watch how these events unfold before moving forward with commitments to new events.

This stance is markedly different from the Saudi actions this year. In rapid succession, the country's various sports and entertainment entities announced new initiatives, making the company one of the largest investors in tennis.

Three separate companies have made tennis investments without much coordination, although outsiders often lump them together.

In quick succession last year, GEA unveiled this Six Kings Slam and PIF announced major new sponsorship deals for the men's and women's tours, which included naming rights for the official rankings. Saudi Arabia's Ministry of Sports, the Saudi Tennis Federation (STF) and the WTA Tour subsequently announced a three-year agreement to host the Tour Finals. Nadal has been named an STF ambassador, helping to promote tennis in the country and give his tennis interests more legitimacy in the eyes of the rest of the world.

PIF officials have been in discussions with executives from Sinclair Broadcast, the owner of the Tennis Channel, about acquiring a larger stake in the network. According to people involved in those discussions who spoke anonymously to protect relations, negotiations collapsed when Sinclair raised the asking price from $750 million to over $1 billion.

These moves boosted Saudi Arabia's tennis profile, but the potential new tournament at the start of the season was considered the most important of its tennis investments – and the most controversial. The event was bid for through PIF and SURJ, but the financial impact almost paled in comparison to the existential dread that permeated tennis when news of the Kingdom's pursuit of the tournament broke. It would cement Saudi Arabia's place at the center of sport and bring with it a widely criticized human rights record.

Announcing the country's agreement to host the WTA finals in the spring, Human Rights Watch said: “The torture and imprisonment of peaceful government critics continues.” Courts hand out decades-long prison sentences to Saudi women over tweets.”

Former players, including Chris Evert and Martina Navratilova, publicly criticized the “partnership with a country with a history of repressive laws against women, that criminalizes homosexuality and free expression and that in 2018 murdered Jamal Khashoggi, a dissident journalist who had traveled to the Saudi consulate. “in Istanbul, Turkey, to obtain documents he needed for a marriage certificate,” he said The athlete wrote in April.

When Saudi Arabia's pursuit of tennis first came to light at Wimbledon last year, it prompted the Grand Slams to launch a counteroffensive that amounted to an attempted takeover of the sport.

Saudi Arabia's entry into tennis has thrown the organizations behind the Grand Slam tournaments into turmoil. (Henry Nicholls/AFP via Getty Images)

Tennis Australia had the most to lose. Any tournament early in the year would have a significant impact on the preparatory events in Australia and New Zealand ahead of the Australian Open.

Led by Tennis Australia, the Grand Slams have come together to propose a new season-long format, with about 14 tournaments included in a so-called “premium tour” for about the top 100 players in the world.

The move was an attempt to separate the biggest non-Grand Slam tournaments from the men's and women's tours. Grand Slam organizers also focused their efforts on players who have long complained about the length of their grueling schedule.

In response, the ATP and WTA stepped up their lucrative sponsorships with Saudi Arabia. These deals generated hundreds of millions of dollars in much-needed revenue for the tours, some of which is passed on to players as prize money and bonuses. Then, at this year's Indian Wells, the Grand Slams tried to pitch their plan to tennis' power brokers but couldn't produce anything fully fleshed out. This idea also faltered, stifled by the inertia and fragmentation at the heart of tennis' corridors of power.

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Since then, top players have again voiced their complaints about the schedule, particularly the tour's decision to extend the duration of several of the mandatory Masters 1000 tournaments from seven to 12 days, essentially turning them into two-week events.

These complaints have increased in recent weeks. Iga Swiatek, the world number 1, complained of exhaustion throughout the summer. Carlos Alcaraz, the sport's biggest young star, predicted in a press conference at the Laver Cup, another exhibition event, that the current schedule is “kind of killing us.”

Adding another event before the Australian Open would result in players feeling forced to hit the ground running, rather than getting into shape in Australia and New Zealand, where they adjust to the time zone in the weeks leading up to one of the year's four tournaments and can adapt the climate to major tournaments.

With the tours failing to deliver what the Saudis had hoped for, plans for the new event and the Saudis' biggest foothold in the sport are still a work in progress. This has allowed sports officials in the kingdom to view the upcoming tennis events as a laboratory experiment.

What happens beyond that remains a mystery.

But what happens next month, from how players experience the event to whether locals and tourists fill the stadium, will determine what happens on a road that is still unfinished.

(Top photo: Adam Pretty / Getty Images)