Mayweather weighed in at 151 and Cotto 154 which is the Super Welterweight Limit.
Casual boxing fans might think that is an advantage to Cotto, but it really isn’t. Mayweather and Cotto are around the same height and to the naked eye Mayweather looked physically bigger than Cotto.
Mayweather is a natural 147 fighter, but he has always come into fights be it at Welterweight or Super Welterweight weighing no more than around 155 pounds come fight night, so don’t expect too much fluctuation between now and Saturday.
You want to be aware of what weight Cotto comes in at on fight night. He looked in good shape, there have been no reports than he had problems making weight, but he did look slightly drain, which is isn’t unusual, but could be a slight concern.
Victor Ortiz came into the ring against Floyd well over 160 pounds and that was a Welterweight bout. I think that hurt him, not as much as him losing his focus, but his punches were not as crisp.
So, just keep an eye on Cotto when he comes into the ring tomorrow.