Manny Pacquiao (53-3, 38 KO) and Juan Manuel Marquez (53-5-1, 39 KO) will meet for a third time later tonight, and it could be the match that sets up a mega-fight between Pacquiao and Floyd Mayweather Jr.
The bout, which goes down at the MGM Grand Garden Arena in Las Vegas, will be available on HBO pay-per-view event at 9 p.m. ET.
Pacquiao needs to make it past Marquez convincingly, and that's no easy task.
They first met in 2004, where the fight was scored a draw after Marquez was knocked down three times in the first round, but then put on the comeback of his life to win enough of the remaining rounds to make it even.
Their second bout from 2008 saw Marquez getting dropped again and fighting back to lose a hard-fought split-decision that many thought he had won.
Since that victory, Pacquiao has gone 7-0 with wins over Shane Mosley, Miguel Cotto, Ricky Hatton, Joshua Clottey, David Diaz, Antonio Margarito and Oscar De La Hoya.
Marquez has gone 5-1 with big wins over Michael Katsidis and Joel Casamayor. His only loss in that stretch was against Floyd Mayweather in 2009.
Round-by-round reaction and results will be posted here for the main event and undercard.