Do not waste your effort on his history at USO. This year for him is like no other and he more than proves it.
Concentrate on what he did during this season as a response to a combined effect of W20, USO20 and RG20.
Remember his serve at AO21? What was it - 'better than ever'?
Then RG21 was a 'sure #21 for Nadal'. And he did a 'dress rehersal' at Rome and then he crushed Nadal tactically mentally and at the end physically,
At W21 he first served 25 aces in a single match, then went into 'least effort Slam win' mode.
So whatever got to him at W21 - food poisoning, anxiety, annoying fans, all of the above- it should be solved and healed by USO21. And his 'answer to question of 2020' will continue, even if it was slowed down a bit at W21.
I expect his serve from AO21 to re-emerge. Maybe a part of it in Tokyo, but at USO in full flight.
If it does - we might see him aim at his AO19 mode - raise in level toward SF and F - and some high level tennis destruction at the end of it - against whoever meets him in SF and F. Kind of - proving that he is worthy of CYGS (Golden Slam?) and #21 - right there at USO, in a country which invented and now is obsessed with GOAT concept.
Win or lose in Tokyo, it decides nothing about USO - this is what he aims for at USO21.
note: Yes, we all know this is sport not engineering, anything can happen, USO is not AO, USO fans are not AO fans, worst day in year, etc etc. This is my personal estimate what he is after given what I know at this moment.