Sergio's last fight at 154: February of 2009
Number of Sergio's title fight victories at 154: 0
Number of former/future/current world champions he defeated officially at 154: 0
Number of former/future/current world champions he defeated there on most scorecards: 1
Cotto's first fight at 154: June of 2010, over a year after Sergio's last fight there, and after Sergio won the middleweight world title.
Mayweather's win over Cotto at 154: May of 2012
Result: Sergio Martinez was the top 154-pounder on the planet, rendering Floyd less than a world-beater and more of a cherry-picker at 154.
You've got to be a physics professor to even explain this thought-process.
Perspective on actual linear time:
The last time Martinez had a fight at 154, that same year, Shane Mosley, Paul Williams and Celestino Caballero were in Ring's top ten p4p rankings. I hope that gives us some perspective on how time actually moves on, even when you don't want it to.