I don't see the challenge for Floyd. Maybe once Amir actually starts sitting down on his punches and changing up his rhythm better, but right now Mayweather woud figure him out in about a round, and after that it would be like Floyd-Mosley but Amir doesn't have the same chin. Honestly Amir is a pretty good fighter with great speed, but he lacks the finesse as a fighter, I have yet to see him be effective on the inside, nor do I see him give a lot of looks to an opponent. Floyd has proven that speed alone won't beat him, because
1) He is just as fast.
2) He has the skill to match that speed.
3) He disrupts your rhythm which means you don't really get to use your speed properly anyways.