You may wanna catch up with the latest chapters to find out more about Nanjirou. His tennis getting consumed is currently kind of not really a possibility imo.
I admit I had a more cynical outlook ever since stopping around Chapter 317, or so a year ago(?).
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With how things are turning out now:
The relationship between Ryoma and Ryoga comes full circle with Nanjiro being their center, and thus this triad sets up the experience of the finals as Konomi’s love letter to his fans on his perception on strong fatherly figures like Nanjiro and their dynamic with their children. Nanjiro may not be the best father outside of his legendary status in tennis, but he did ultimately pave the way for both his sons to explore options past their homeland. So both brothers are representations of experiencing a cultural melting pot, and the tournament extends how they react and use that liberation; it also serves as a rite of passage.
Ryoma can borrow the ‘genius’ behind every player he faces and watches, and has a vicarious identification with this to adapt and grow organically. Compare this with Ryoga, who is the complete opposite like I mentioned in my previous post; consuming everything he can with little care of the sentimental value, and seems to be nihilistic about tennis.
Team Spain is Nanjiro’s way to have that indirect battle with both his sons, and to also prepare them a team that would take his prime and develop from that which makes this triad come full circle; not just about whose tennis is superior, but the resolve they have over it. It’s the best way a father can have assurance over his legacy by simply showing his influence towards others outside his family, and seeing where their competencies can take them. It also is Nanjiro’s way to see how both sides of the coin with the brothers are also how he could’ve turned out if he had to choose either path instead of dropping the personal dream early and passing the torch to his legacy.
That decision probably prevented this from being a fatherless shonen on Konomi's part because it would've ruined his message. So Nanjiro is a bit of an insert for him, but I see this as a good thing.
Because ultimately, like Nanjiro said to Ryoga to only take things seriously with Ryoma when he’s a competent player. At least Ryoga has a redeeming quality to respect his father’s wishes. One thing that I’m curious about is if Ryoga’s nihilistic view on tennis is authentic, or a ruse to raise the stakes.
This is why, even to this day, this franchise holds a special place from within for me.