After Mayweather beat Oscar he said he wanted Martinez. I laughed because Steward and Merchant were commenting on Mayweather not wanting to fight the current welterweights because they were to big. Soon after Mayweather said Martinez was too big. Not the op asks why Manny, a former flyweight will not fight a middleweight that the bigger Mayweather wouldn't.
Who said Sergio was too big for Pac? Its just Pac has wins in 8divisions and Pac may be content with that. Pac may may do better against Sergio than Cotto though.
But Cotto is closer in size to Sergio than Pacs, of course he is. Theres a thread on this already.