We can say that a boxer who aged will definitely lost their speed first, that's what happen to Roy Jones Jr, in his prime, damn, Roy was one of the fastest if not the fastest boxer I have seen. Not only fast but has power behind it. Same with Manny Pacquiao, we've seen that he has deteriorate in the years after being knock out my Marquez. Yes he won some fights after that, but the he was a tad slower. Same with Donaire, and then he fought a version of Inoue which is on the prime years of his career, so it's hard to beat that combination, young and power and speed.