People are thinking that Mayweather is the 35 year old Mayweather. He is not. He is the 41 year old Mayweather. He was retired. He was not anticipating fighting again. Sure he had a few months to prepare, but when your mindset is not in keeping in shape, you will not get in the same shape ever again, especially at his age. It is a mental thing.
It will be close early as Mayweather will run and box to stay out of reach of McGregor. McGregor will need to use his strength to hold and hit Mayweather inside. And not use all his energy to go for a knockout early. If he traps Mayweather and mauls him and goads him into that style of fight, McGregor will win. If Mayweather runs the whole fight (and I don't think he can be in that kind of shape to do that) and boxes from the outside, he will win. A clash of styles that makes this fight interesting.
I am predicting a McGregor win and a bloody win at that. However, the style will make the fight. Whoever is the strongest mentally will overcome.
p.s. the above evaluation is based on a fair fight. My 2nd prediction is that Mayweather needs the money and is going to dump. Let's see if I am wrong twice.