Zilina is a pretty town of squares and churches with a population of a little more than 80,000 that sits at the confluence of three rivers in the mountains of north-west Slovakia. It was, frankly, an incongruous place for a revolution in English football to begin, but it was there in 2003 that Chelsea played their first game under Roman Abramovich, a routine 2-0 win over MSK in a Champions League qualifier. Their last may come at Norwich in a couple of weeks, or perhaps at home to Brentford a fortnight after that, depending how soon a buyer emerges and how quickly the deal can be finalised. But it will be soon and, a couple of months after completing the full set of possible trophies by winning the Club World Cup, the Abramovich era at Chelsea will be over.

The legacy he leaves is complex, not least because it is very hard to assess when it is still not clear why he bought the club. From a purely footballing point of view though, he brought Chelsea huge success. The temptation to point out that he took on a club that were fourth in the league, spent £1.5bn and leaves them third is strong, but Chelsea now are a very different club from the one he bought. They are no longer the flaky mavericks of the Kings Road, but an indisputable superclub. They had won the league only once before he arrived but he brought them five further championships, along with two Champions Leagues, five FA Cups and three League Cups. Might they have won more with more patience? Perhaps, but that is an enviable amount of silverware.

He also changed football utterly. Chelsea beat Leeds 1-0 in the last game of Abramovich’s first season, after which Claudio Ranieri performed a slow, tearful lap of honour. Around £153m had been spent on players in that first year, £150m would be spent in the second – unprecedented sums at the time – and José Mourinho appointed manager.

Seven miles to the north-east, Arsenal celebrated the completion of their Invincibles season with victory over Leicester. For them too, the future seemed ripe with possibility. Three months earlier, work had begun on a new stadium. With a capacity more than 50% greater than that of Highbury and an array of corporate facilities, this would allow them at last to compete with the financial might of Manchester United.

The problem was, the world had changed. Chelsea didn’t need a big stadium; they had Abramovich. Spending power, suddenly, had become detached from success on the pitch or the capacity to generate revenue through vast crowds.

Abramovich has always denied buying Chelsea for any reason other than love of football. That may be the case. But what is certainly true is that he paved the way for other owners whose wealth dwarfed that of even the most successful traditional owners, for the sheikhs and public investment funds whose interest in football was not winning trophies or even making money but massaging their public image.

Roman Abramovich with the Club World Cup trophy
Roman Abramovich completed the full set of trophies after celebrating Chelsea’s Club World Cup triumph. Photograph: Michael Regan/Fifa/Getty Images

What happens next probably depends on who buys the club from Abramovich. Perhaps the process will be smooth, and Chelsea will simply swap one billionaire for another. But that is by no means certain. Much of Abramovich’s statement that the club is for sale was unclear. He may be writing off the £1.5bn the club owes him, but is that factored into the price? And could that leave the club liable for a substantial tax bill? And what would be the financial fair play implications of that? When he says “net proceeds” will be donated to a charitable foundation, net of what?

There have been clubs sustained by a single wealthy owner before and it’s unlikely problems would be as severe for Chelsea as they were for, say, Blackburn, still less Gretna. The past 19 years have been an era in which their successes were broadcast across the world. They have a worldwide fanbase that should make them an attractive proposition.

But the issue of the stadium is limiting. Hemmed in by a cemetery on one side and a railway line on the other, it is very difficult to increase the capacity of Stamford Bridge from 41,800, and various attempts to move over the past 20 years have come to nothing. A big stadium is not essential to a modern superclub, and it is certainly not sufficient to be one, but obviously the more revenue that can be generated on matchdays, the less burden there is on an owner. Other billionaires may not be so prepared to fund the club as Abramovich has been.

There’s also the threat of a change to the loan system. Chelsea have 23 players out on loan, but have often in recent years had more than 40, largely as part of their policy of developing and selling young talent. From the summer the number of players a club can loan out will be restricted, which potentially cuts another source of revenue for Chelsea. The European champions may not be such an attractive proposition as they initially seem.

With Chelsea’s future so uncertain, perhaps others will reconsider the wisdom of judging suitability for ownership purely on the grounds of wealth. At the very least, football should be contemplating the road that led from Zilina to this absurd situation whereby military decisions taken by foreign governments can have such an impact on an English club, and wondering what it could have done differently.