As Manchester City prepared to face Leicester on Boxing Day, Pep Guardiola had a problem.
It is well documented that his City side is very much about the collective rather than the individuals. Guardiola has assembled a well-oiled machine made up of multiple co-dependent parts which can be swapped out for others as circumstances dictate.
However, it doesn't take a genius to work out that Rodri is the player most crucial to how Pep wants his side to play.
The holding midfielder has come on leaps and bounds since enduring a tough first season in Manchester. While his awareness and passing left a lot to be desired that year, the problem was just as much the system as it was his own game.
In 2019/20 City did not play to Rodri's strengths. He was repeatedly left exposed to counter-attacks, with the burden of dousing out the fires - something Fernandinho has always been better suited to - placed firmly on his shoulders.
This season, Guardiola has perfected a system to get the most out of the Spain international.
Playing in a number six role - a position usually associated with chance creation from deep - Rodri attracts the attention of pressing attackers in order to free up space for the inverted full-backs on either side of him.
The 2-3-5 system that City tend to use when in possession means that Rodri always has at least one free man to pass to, and if not then an attacking midfielder - usually Bernardo Silva - drops deep to create a numerical advantage and offer a passing option.
The problem with the effectiveness of Guardiola's latest tactical tweak is that it is has seen Rodri eclipse Fernandinho - by some distance - as City's best holding option. City's club captain may be a more combative midfielder, but Rodri is a level above in terms of passing, vision and positional awareness.
Perhaps Rodri's better grasp of the role is understandable; after all, Fernandinho has had to relearn his position in his mid-30s.
This season it has become painfully obvious that City play nowhere near as well when the Brazilian deputises for his younger teammate. Before the 6-3 defeat of Leicester, City had lost four of the six games Fernandinho had started this season.
But as he did against the Foxes, the 36-year-old showed against Brentford that he may have fixed Guardiola's and City's biggest flaw.
The 10-minute horror show against Leicester notwithstanding, City haven't looked like they've missed Rodri that much. On Boxing Day, Fernandinho coped well with a team renowned for its counter-attacking threat and in west London he was superb.
His performance showcased all of the Fernandinho trademarks City supporters know and love - the intensity, the tactical fouls, the passion.
He was predictably sound both in defence and attack, but what was most impressive was how City still managed to control the game - through possession of the ball - with him in the side. Usually they don't, but on Wednesday he got his positioning and link-up with inverted full-backs Joao Cancelo and Nathan Ake spot on.
Of course, once Rodri is fully fit he will assume starting duties, and we may not see much more of Fernandinho this season. Yet just as some were beginning to think the City skipper had stuck around just a year too long, he has proved he still has what it takes.
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