As someone mentioned earlier, at their primes at lightweight...Floyd vs. Shane would be a dream match up. Or the Shane that fought Oscar in their first fight vs. Floyd would also be pretty incredible. Shane is still a tremendous warrior (i had his fight with Cotto a draw), but he looked noticeably slower in the Cotto fight...and his blazing speed and athleticism where his biggest assets. He still would be no pushover against Floyd now...but Shane in his prime would be a tremendous challenge for Mayweather.