What I find fantastic about this series is the degree of craftsmanship the author shows in creating the protagonist.
I don't read sports series often, but the genius trope appears in other genres of manga and it's fairly well-defined: we have the arrogant geniuses who are charismatic and the natural leaders of their teams. They may be more or less abrasive, more or less villainous, but we can guess what the flashback arc will show about them: how their natural talents were overwhelming since the beginning, and how it went to their heads.
Then we have the lonely genius, who isn't particularly charismatic or sociable, and whose talent causes everyone to keep their distance. They're taken for granted, and like the arrogant genius they tend to underestimate their opponent, usually the underdog protagonist who's all about hard work and passion, because they don't really contemplate the possibility of being beaten.
The author of this series is doing something very different. It's a very twisted form of the detached genius: one that will never underestimate an opponent because he's guilt-ridden by the idea he might have destroyed friends' careers and crushed their ambitions, and thus has grown paranoid about winning lest his former opponents' own struggles are rendered meaningless. It gets to the point that he drives himself lonely because he can only rely on himself to carry a cross of his own making. He'll never be defeated by lowering his guard against an underdog hard worker, because he's an extreme hardworker on top of being a prodigy, and because he will give his utmost at every single pitch. Like the old adage about a tiger using all its power to hunt a rabbit, Jiro will never lower his guard against Yamato. Which means if Yamato is to beat him, he'll have to really outclass Jiro.
The best thing of it is that all the story is about how a mindset like his comes into being. Instead of introducing him fully-formed, the author makes painstakingly credible how and why Jiro has become like this. He gives him a supportive family, three older sisters who like their little brother without being doting or overprotective, and a gentle disposition. So we know from the beginning he doesn't want to hurt anyone's feelings and that he struggles with peer rejection.
And then we follow him through a gradual, painful journey where he tries every single strategy to be accepted, only to end up realising he'll have to settle by one close friend - Yamato - and be set apart from all the rest because of the mission he has given himself.
It's frankly exhilarating to read. The author didn't need to use any twist like amnesia or time traveling or revenge to create a unique mindset in a protagonist. He just put together traits that would make a bad match for the environment around the boy, and let the traumatising experiences write themselves, and drive him into a corner. It's not even easy to put my finger on one wrong decision, or to imagine how things could've been different. Jiro truly drew the short stick due to who he is.
Character building doesn't really get any better than this. The narrative technique is also flawless. I'd say this is one rare case of a perfect manga. I just hope it remains that way till the end.