He was able to beat pacquiao, after pacquiao had learned from his previous 2 ko's, those 2 kos were when he was new then he started learning and getting better.
until he was dominating, then he had a chance against the mexican legend and that time erik morales thrashed him, he was faster then him and more clever in using combos but it was a great performance from pacquiao.
it was at that time morales defeated the rising and dominating start pacquiao, which after pacquiao had a chance after ending up in his favour.
pacquiao's 2 losses was when he was starting and after that he had an unbeaten streak from then on and after defeating barerra at that time when he was good, after morales defeated him.
so that is how he will be remembered as the one that defeated pacquiao.