Irrelevant. I guess the reason you basically never see fighters fight 9 weeks after a fight is because its not a handicap right? Maybe you need to educate them.
1. Fighters fight every nine weeks or less all over the planet. It's normal. 2. It rarely happens at the top level in modern boxing because time and energy must be afforded for promotion and securing venues and broadcasting slots. Kovalev never disclosed any sort of injury that he entered the Canelo fight with. Ironically enough, Andre Ward fought most of his later fights with serious injuries, but never lost a single one of them.
It rarely happens at the top level because its sub optimal. You could organise promotions months in advance. The body needs to physically heal and rest between fights especially tough ones. Injuries? He was almost knocked out 9 weeks earlier and was 36 years old. The body needs time to heal and recover from that kind of wear and tear its not about a specific injury.
You want a source for the most obvious thing in the world if you understand anything about boxing? I already gave you a mountain of evidence. Its unheard of for top pro fighters to fight 9 weeks apart. Its because its not good.
Your claim does not even make sense. If a fighter gets paid every time he fights, and generates a profit for the promoter, then they be incentivised to fight every 9 weeks if they could. Money is inventive to fight more not less.
If Kovalev beat Canelo he'd have probably been in contention for fighter of the year. He was not shot. It's a good win and would be perceived better if not for Kovalev's quick turnaround. Kovalev had taken two very impressive 0's that year already.
Not that impressive in retrospect tho are they.. Alvarez was sparked by B- level Joe Smith (both Bivol & Beterbiev wiped the floor with him) & hasn't fought since .. & Yarde still hasn't beaten a single fighter of note despite turning professional nearly 10 years ago. At the time they both looked like quite decent wins but not now. When you are young in your career and coming up you can have that quick type of turnaround because the opponents are poor .. but when you fight at the elite levels nowadays (especially in your mid 30s) & after years of conditioning your body to a regime of 6 months between fights a quick turnaround will have a detrimental impact in your performance. Prime Kovalev would have pinged Alvarez all around the Ring in my opinion.