ithink you're mis-remembering the fight. martinez didn't look as bad as you describe except for the second half of the first round when cotto was battering him....martinez actually tried to mount a rally and was boxing decent for about a good three rounds (rounds 3-5)...yeah, the knee was a problem, but now ALLthe talk is about his knee people wanna act like martinez looked like he needed to be on crutches the whole night. that's just not true.
Rounds 3-5 he was doing marginally better, but Cotto also let up because he felt bad for Martinez. Cotto could have knocked his ass out way earlier but let him mount a last hurrah because he knew Martinez's career was done just by his body language.