Differences in speed

A question here for people who are well acquainted with boxing: After watching Pac-Marg, I became a worried. Not for myself, but for Amir Khan. I need your help explaining something ... Amir is credited with a lot of speed, and so I began to wonder. Is the difference in speed between Amir-Maidana greater than the difference in speed was between Pac-Marg? I ask because even though Pac looked a lot more mobile than Marg, he still ended up on the ropes a couple of times and had to deal with some tough flurries from Marg. Am I to assume that Khan WILL get caught with a few punches like Pac was? I'm guessing Pac moves around the ring better, and he still had to deal with tough contests at the start of the fight. If Khan does get caught, I'm really quite scared for the guy, as I like him. I get the impression that he'll end up on the ropes a few times and I'm guessing Maidana might be quicker and more mobile than Marg was? However, this is conjecture as I haven't seen enough boxing to be able to say. Any help on this talk of Amir's speed and how it actually translates to Dec 11, would be appreciated!