Manchester City's Carabao Cup win at Oxford in 2018 will be remembered for Phil Foden's first goal of many for the club, but it also featured another significant selection from Pep Guardiola.
In a game against League One opposition, Guardiola rotated and experimented, with Foden, Aro Muric and Brahim Diaz starting at the Kassam Stadium.
When the City team sheet was revealed, fans may have thought Guardiola would offset that inexperience with a back five as Vincent Kompany, Nicolas Otamendi and John Stones were all named in the starting line-up.
Stones would be used in defensive midfield, though, as Guardiola continued an experiment tried off the bench a handful of times previously of using the former Everton man as a shield for the defence.
Given Oxford's level, Stones got a feel for the position, but didn't give much of an indication of whether it would be a useful plan B going forward.
Later games against Crystal Palace in the league and Leicester in the cup signalled the end of the experiment and Stones would return to battling with Otamendi to partner Kompany.
The following year would see Stones struggle to get into Guardiola's side at all, but he recovered last season to form an impressive partnership with Ruben Dias. Now, with Aymeric Laporte back in his best form, Guardiola finally has three world-class defenders, all playing well, competing for two spots.
So how does three go into two? Rotation is fine when the games are regular Premier League or cup fixtures, but once the big matches come around those three players will all be expecting to start.
In recent weeks, it seems Guardiola's solution is to start all three - but to shift Stones out to right-back.
It's a position he's deputised in before, but never been a regular. Yet in four of his last six starts for City, Stones has been deployed at right-back with Dias and Laporte in the centre.
Injury and suspension have forced that selection in at least one of those games, but on Saturday at Everton, and previously against Brentford, there were two other full-backs on the bench.
Guardiola has pointed to Stones' height and aerial presence as justification for playing all three centre-backs, while he was clearly unhappy with Kyle Walker against Tottenham as he dropped to the bench at Goodison Park.
Walker may face a challenge to regain his place, as Stones has four clean sheets from four outings when playing at right-back. It seems Guardiola has decided that Joao Cancelo is predominantly a left-back for the time being, so perhaps Stones is now the second choice on the right.
He looked unfamiliar with some aspects of the role at Everton, particularly in attack, but fared well defensively and has proven to be a solid option if required. His passing to link up with his winger and right-sided central midfielder is improving and maybe right-back is his best opportunity of games for the moment.
It's another show of faith from Guardiola that he is willing to trust Stones in such a key position in City's system. There were times over the last year or two where Stones wouldn't have had the confidence or backing to be exposed so much, so it's a credit to himself that he's able to change position with ease.
Right-back may not be Stones' future position at City, which will remain centre-back, but perhaps these full-back experiments are auditions for Guardiola to revisit the previously-abandoned defensive midfield plan.
Stones wasn't ready to take on the tactical responsibilities of playing in holding midfield in 2018 and hasn't been in the right form to try again since then. Now he's showing promise with the ball on the right, could Guardiola be tempted to revive his forgotten plan for Stones' evolution?
With Fernandinho out of contract at the end of the season and Ilkay Gundogan the 'wrong side' of 30, that is a position that will need replacing in the next two or three years.
If City want to buy time, they can extend the contracts of Fernandinho or Gundogan, and may also be able to use Stones as cover from time to time.
Players like Cancelo, Aleks Zinchenko and Gabriel Jesus have kickstarted faltering City careers by changing position, so maybe Stones can use his position of strength as an in-form player to keep his options open going forward.
Guardiola has a history of knowing the right player to shift around at the right time. Three-and-a-half years after the idea first came into his head, could Stones finally be ready to learn that key midfield role?
