Floyd already dominated more talented and skilled fighter. (Zab Judah) Floyd could fight aggressively against faster opponents. He would box Amir Khan's ears off.
Floyd ducked Khan. Don't think he had power to KO Khan, so it's entirely possible that Khan could have beaten him on activity if the judges were on the up and up. I'd go Floyd by decision, but there's a reason Floyd swerved him.
All the Floydettes had him KOing Maidana (to the body) and Cotto (on cuts). Maidana took him to the brink while being forced to wear different gloves and Floyd also knew he lost. Cotto took him deep as well.
Khan would give a good account of himself however Floyd takes over from halfway with the rounds split or 4-2 Floyd. Come 8th and 9th round Khan makes mistakes with Floyd catching him regularly. I see Khan getting stopped due to an accumulation of accurate punches.
Khan of all the people a bloke with far less skill against the consummate skills, know how, speed and timing of Floyd alongside Muhammed Ali the most accurate boxer ever.
Floyd would have fought after Maidana 1 but the money fight became the rematch and Khan was so desperate it was funny that Floyd played with his head and mind.
Khan starts fast, but loses a decision as he can't adjust to Floyd's adjustments. Floyd would figure him out after 2 rounds.
Since when did it take a huge puncher to stop Khan? Floyd while not being a huge puncher he hit hard enough to keep fighters honest. There is a reason opponents couldn't just walk forward at will and walk him down.
It's disrespectful to Floyd Mayweather to even ask this question. There's levels. Khan would always have had no chance