There likely aren't two rival fighters in recent memory who know each other inside and out the way Manny Pacquiao and Juan Manuel Marquez do. After engaging in three all-time classic bouts in the past eight years, producing three contentious and strongly debated decisions, the two will square off Saturday in Las Vegas for what will likely be the final time. And depending upon how you scored each of the first three bouts, whichever fighter wins No. 4 could very well lay claim to having won the rivalry. With his timely counterpunching and legendary determination, Marquez (54-6-1, 39 KOs) has been nothing but trouble for the aggressive Pacquiao (54-4-2, 38 KOs), who has relied on activity and a power-punching advantage throughout the rivalry.

Below, our panel of ESPN.com experts picks the winner of the main event, predicts the knockout of the night and pinpoints the undercard fighter who has the chance to help himself more than any other on Saturday.