The notion of a fixture being a derby used to signify geographical proximity. Now it tends to relate to any common denominator between two clubs. Even so, Manchester City against Leicester City might be a derby with a difference on Saturday if it is jokingly branded "the Riyad Mahrez derby".
The Algerian definitely will not be playing for Manchester City after City failed to sign him at the end of the transfer window. He surely will not be lining up for Leicester either after missing training in response to Leciester's refusal to sell him for under £95 million. A game may be defined by his absence, perhaps even decided by those filling the roles that might otherwise have been occupied by Mahrez: Fousseni Diabate or Demarai Gray for Leicester, Bernardo Silva for Manchester City.
The temptation is to wonder if Mahrez is still at East Midlands Airport, waiting to board a flight to Manchester. Metaphorically, he could be. He seems stranded in limbo, with some wondering if he will play for Leicester again. If the initial sounds from Manchester City were that their interest could be renewed in the summer, they could scarcely say the opposite. To present their attempts to sign him as a knee-jerk reaction to the loss of the injured Leroy Sane a couple of days earlier would imply such a costly short-termism that they were willing to pay £60m for a few weeks of Mahrez before presumably benching him when the German returned.
And perhaps Pep Guardiola will be back. Perhaps Leicester will lower their price. Perhaps Mahrez will swap one City for another. Certainly there is the expectation that the champions-elect will bolster their forward line in the close season; they would have done so last summer had a similarly late move for Alexis Sanchez succeeded. And Mahrez, with eight goals and seven assists, is the most productive player outside the top six. His return in 2015-16, when he won the PFA Player of the Year award and contributed 17 goals and 11 assists, suggests it is no outlier.
And yet there are reasons to believe Mahrez is far from Guardiola's perfect player. True, he has experience of working with a left-footer who would veer in from the right flank and Lionel Messi turned out alright as a false nine. If comparisons with Barcelona's record scorer are inherently unfair, they may also be irrelevant. It is worth remembering the forward Manchester City had targeted was Alexis Sanchez; Mahrez is scarcely a duplicate of the quicker, more direct, more prolific addition to Manchester United's forward line.
Nor is he a replica of Sane, whose ability to stretch the game by offering width has made him invaluable. Guardiola's positional game is based in part on making the pitch as wide as possible to free up room for Kevin De Bruyne and David Silva in the middle; Mahrez's signature move is to skip inside. Perhaps, were he to occupy his Leicester role on the right, it would allow Kyle Walker to overlap. Yet City's current right winger is Raheem Sterling, scorer of 19 goals.
Look at the five current forward options, when all are fit, and three seem more obvious Guardiola players: not Sergio Aguero, the specialist finisher, or Bernardo Silva who, like Mahrez, would have been an inside-forward in earlier generations, but the natural wingers Sane and Sterling and the striker Gabriel Jesus, whose high pressing his manager has described as the best in the world; Mahrez, in contrast, has never been known for his defensive work and benefited from having the human dynamo N'Golo Kante immediately inside him on Leicester's title-winning team. If Guardiola likes young players, it is because it is easier to mould them, while Mahrez will be 27 soon.
So life at the Etihad Stadium could be a culture shock. Mahrez is accustomed to a very different style of play. There is a world of difference between Leicester's 45-percent possession model -- though up to 46 percent this season under the quiet evolutionary Claude Puel -- and Manchester City's 70-percent blueprint under Guardiola. It is reflected in his passing statistics; Mahrez's completion rate of 75 percent this season is lower than every player in Guardiola's squad. That may highlight that Leicester have fewer passing options and the imperative of heading for goal quicker in their tactics, especially given Jamie Vardy's fondness for quick counterattacks; Mahrez averages far more long passes per game than any of Guardiola's midfielders or forwards apart from De Bruyne.
But his game would have to be recalibrated at the Etihad Stadium. That is not impossible, just as Arjen Robben has shown a goalscoring left-footed, right-sided winger can flourish under Guardiola. But Mahrez would have to adjust to an environment where he was not the premier talent and the team was not built around him. Perhaps his desperation to move shows a willingness to do that. Yet there seem more logical fits for a Guardiola side elsewhere. The league leaders' January interest looked like a pragmatic bid for the most productive performer outside the top six. Summer is a bigger window that offers broader horizons and the chance to find the perfect player for Manchester City's game plan. Despite his considerable quality, it may not be Mahrez.