Every GSP fight you will notice his opponent come out "fighting". But at the end of the fight, that fighter will leave "defending".
In GSP fights the first couple rounds you will see defeat phase in and his opponents will do less offense and more defense. It tends to turn into 100% defense very fast.
Tonight Diaz showed some good defense. But nearly all of the offense was done by GSP. Like most people, Diaz knew that if he opened up too much GSP would capitolize and win the fight easy. Opponents of GSP tend to notice they are going to lose very early and decide the new game plan is to simply "stay alive".