Well out of the original G10 is pretty much Byodouin >>> everyone else based on what we know so far. Obviously the current #4 (Ryoga) and #5 (Oni) are way stronger than a person at their position ought to be.
So I don't think Kaji needs to be particularly amazing to earn that spot, since losing badly to Oni shouldn't be a strike against your power. That's why it particular sucks for him since he must have thought he got that spot due to his hard work/talent/whatever and then it turned out to be a cruel joke. Yes #4 is in the same boat, but he was just flat out unlucky. Him losing to Ryoga is no different than say if he got ran over by a car while overseas and never returned. It's a simple Act of God that's unavoidable. In Kaji's case, it seems like he's just a victim of someone's idea of a joke.
I have a feeling there was no No.4 at all.
The coaches said "Who's this?" when they saw Ryoga, instead of
"Where the heck is the No.4 who is just 17, therefore his parents are going to be worried sick that we left him overseas and we're going to get our asses sued!!".
So for that reason, I think No.4 really was Irie/Tokugawa. And they have no respect for their country.
Oni got No.5 like... A year or two ago.
Kaji lost to 10Ball!Oni, or he lost to Kishin!Oni.
I think its the latter since No.6 Ohmagari gave zero shits watching 10ball from Oni.
I think the gap between No.6 and No.7 is like the gap that MUST exist between No.14 and the rest of No.15-20.
This is because Nationals!Tooyama > Oni only using BJK and Hakamada >> Nationals!Tooyama.
And No.18 & 19 shat bricks when they noticed BJK being prepared.
So Kaji has the saddest story. It really means Byoudouin and Duke wanted to have a laugh.
My issue is that No.6 to 10 gave zero shits that Kaji was gone.
So was Kaji stronger than Ohmagari all the way to Mouri?
Since I think Kaji deserves some respect, if Hakamada > Nationals!Tooyama, No.14 all the way to No.6 must be pretty good.
I expect Ban to be not better but at least the same as Hakamada,
No.12 was obviously better,
No.11 was either equal or extremely close to Nationals!Yukimura, No.10 I expect to not be better but at least the same as Fuwa
Ochi was obviously slightly better than Mouri, and Tohno and Kimijima showed no doubles specialties so they are just individual greats forced into Doubles so have to be a tiny bit better than Ochi.
Ochi cannot drop his service game against Niou and Atobe but he can take at least one service game from Niou and Atobe with Mental Pressure.
So we're looking at Kaji being above Niou and Atobe in Singles. Remembering Atobe couldn't return Mach serve consecutively.
So no matter what, Kaji's abilities deserve respect. For him to take out BJK!Oni and the Oni we saw looked like a got damn demon, implying Kishin Mode, Kaji has to be really strong.
The guy has no got damn pupils like Kishin Mode.