floyd mayweather and manny pacquiao came close to a fight in 2010 .
the pair will finally meet in at the mgm grand in las vegas on may 2 .
trainer freddie roach believes mayweather is slower than he used to be .
pacquiao will attack mayweather and knock him out , according to roach .
watch here : mayweather vs pacquiao official advert released .
amir khan : mayweather and pacquiao have n't even heard of kell brook .
click here for the latest mayweather vs pacquiao news .