Let's say he beats Cotto then Martinez or Manny later in the year. Between Khan and Saul who do you want to see as his last fight?
If those 2 are the options, easily Khan. He's more proven and brings an interesting style to the table. A wannabe pacquiao that substituted the cross for a jab is unique compared to Alvarez. Alvarez has shown to be a generic latino boxer-puncher so far. Mayweather has already beat up enough of those in his career. Cotto(e) is poor man's Oscar. Alvarez is poor man's Cotto(e) who thinks extra hard and tries to be real deliberate during fights.
