A day after Stoke City, a team who used to revel in their status as unpopular underdogs, were relegated from the Premier League, it was fitting that Cardiff City sealed promotion.

Most seasons the Championship throws up an unexpected success story, a team that scraps its way towards the top of the table as everyone waits for the bubble to burst. Last season it was Huddersfield and Reading, the season before that Sheffield Wednesday.

This time it has been Cardiff but, while the teams in previous years have managed to cling on and claim a play-off place, the Bluebirds are up automatically, trailing only the juggernaut of Wolves. A decent season for Cardiff would have been a top-half finish. Top six looked achievable but very ambitious. This has been utterly extraordinary.

And in a way it is all thanks to the Rotherham chairman, Tony Stewart. Back at the start of 2016 Neil Warnock, his enthusiasm for the game dimmed and mind elsewhere after his wife Sharon was diagnosed with cancer, was not really looking to get back into management. But he was invited to a Rotherham game and eventually persuaded by Stewart to take over and save them from relegation. He duly achieved that but, more importantly for Cardiff, it reignited his taste for management and, more specifically, for an eighth promotion.

Cardiff are the fourth club Warnock has taken to the top flight, something no other manager has done. While it is always handy to take what the 69-year-old says with a soupcon of salt, given his team were second-bottom when he took over last season, one can believe it when he says this is his greatest achievement “by an absolute mile”.

They finished the season on 90 points, three more than when they were last promoted in 2013. That year it was enough to win the Championship. It is also their highest tally since three points for a win was introduced in 1981, the second-highest ever if the 1947 Division Three South winners’ total is adjusted accordingly.

It is all the more remarkable considering the teams they have finished above. Middlesbrough, Aston Villa and Fulham all have the financial means to augment their squads with Premier League quality players. Cardiff have spent money – Gary Madine somehow cost them £6m in January – but their success has not been based on it.

Their best performers have essentially been reclamation projects, unpolished gems and those unwanted elsewhere. Junior Hoilett was signed on a free transfer, as was Sol Bamba. Sean Morrison was discarded by Reading four years ago. Nathaniel Mendez-Laing was signed from Rochdale. The goalkeeper Neil Etheridge came in from Walsall. Callum Paterson was bought as a right-back but converted into a midfielder. One could go on.

This has been the source of Warnock’s strength this season and indeed down the years. He excels in bringing together jigsaw pieces that do not fit and making sense of them. It has been one of the most extraordinary examples in recent years of making a team more than the sum of its parts.

Warnock’s methods are not especially complicated, broadly based on team spirit and bonding, and an underrated aspect of it is how he has managed the expectations placed upon them. When promotion started to look plausible, then likely, with pressure theoretically growing, Warnock emphasised that, even if they had to go through the play-offs, it did not matter too much because they had already had a great season.

Then there is their rather straightforward style of play. What constitutes entertaining football is entirely subjective, and the unattractiveness of Cardiff’s football this season has been exaggerated by some. They do have decent ball-players in their team and will almost certainly buy some more, but this is not a side who will win prizes for aesthetics.

Only Burton, who were relegated, Bolton and Millwall had a lower possession rate. Nobody played fewer passes, nobody completed fewer passes and nobody played fewer passes in the opposition half. Nobody won more aerial duels, nobody had more efforts on goal from set pieces, only Bolton committed more fouls. In short a Premier League fan unfamiliar with Cardiff should not prepare to like them.

The question now is whether Cardiff can translate this success to the top flight. Their style of play should not be a problem in that respect: it is not a million miles away from Burnley’s, whose achievements Warnock has said he would like to emulate.

For now, though, this is a good enough achievement. As an image to sum up how extraordinary this promotion is, consider the sight of Vincent Tan, formerly one of the most hated owners in football, being carried shoulder high by Cardiff fans after the 0-0 draw with Reading that confirmed their promotion on Sunday. Cardiff in the Premier League could well be rather fun.

• This article was amended on 8 May 2018 to cut a phrase saying that Neil Warnock’s achieving of eight promotions was something “no other manager has done”.