I'm going to watch every Floyd Mayweather fight: TKO1 Jerry Coopoer

Part of the issue with Floyd's level of aggression was his hand problems. He broke his hand against Carlos Hernandez pretty badly. His shoulder was also injured in the first Castillo fight as you note. Although post Castillo he was aggressive against Ndou, Corley, Gatti. Against Judah he struggled with Judah's speed losing the first few rounds before adjusting and walking Judah down. It should be noted Corley really hurt Mayweather, I'm not sure people remember that now and the same round IIRC Mayweather walked Corley down. Corley's a bit underrated as he really hurt Cotto too, despite the fact he gave up something like 18lbs in the ring, but that weight draining won't have been great for Cotto's durability. I think Torres put Cotto down a few times IIRC and Bob Arum said he hoped Cotto was more careful going forward. They probably should have moved him to 147 much earlier, where he's healthier.

I think Floyd isn't great against southpaws. He doesn't entirely get the angles quite right but gets away with it because he's so good. But he never really timed Pacquaio the way Marquez was able to because his angles/footwork are a little off. I'd say Marquez and Hopkins are the best examples of boxers who get the angles perfect against southpaws