From the bits I've seen of the fight, looks like he just walked him down and stopped him as per his usual style.
I think Sergio had an off day when he lost to margarito. He wasn't too sexy for his opponent that night.
Margarito only performed so well because he was angry at Sergio for making him question his sexuality. Tony was all homophobic rage in that fight.
ANTONIO sure has a lot of self control. HOw he managed to NOT GO FOR THE LOW BLOWS, the world will never know.