LAS VEGAS -- The rivalry between Manny Pacquiao and Juan Manuel Marquez, which has stretched across nine years and three brutal fights, has left boxing fans with indelible memories of their violent confrontations and the fighters with no more or less personal passion for each other than when they started.

As they head into a fourth fight Saturday (HBO PPV, 9 p.m. ET, $59.95) at the MGM Grand Garden Arena, both are hungry for a definitive victory in a series that so far has produced three controversial decisions: a draw in a 2004 featherweight championship fight, and two incredibly close wins for Pacquiao -- a split decision in a 2008 junior lightweight title fight, and a majority decision in a welterweight title fight in November 2011.

Yet through it all, Pacquiao (54-4-2, 38 KOs) and Marquez (54-6-1, 39 KOs) have remained all business with each other, evoking neither love nor hate.

"I don't think they feel anything [toward each other.] I find not even a hint of interaction between the two," Top Rank's Bob Arum, who has been the promoter or co-promoter for each chapter of the series, said before the final news conference Wednesday. "I think there's maybe some animosity on Marquez's part because he didn't get decisions he thought he was entitled to, but he doesn't hold it against Pacquiao. And Pacquiao respects Marquez. What's not to respect? But there's no real feeling between the two that I can sense. Nothing."

Freddie Roach, Pacquiao's trainer, also sees no particular relationship between the fighters.

"They're both gentlemen. They have no dislike for each other, but they're not friendly, either," Roach said. "There's just no emotion. They're not bad with each other, but they're not overly friendly. They'll say hi to each other and that's about it."

To Marquez, his relationship with Pacquiao is easy to explain.

"I think that the relationship with him is one of respect," Marquez said. "It is a professional relationship and the last three fights we have had were wars, so I know he respects me and I respect him."

So often in boxing, fighters who face each other multiple times develop some sort of lasting bond, for good or bad.

Sometimes the fighters become great friends, as Micky Ward did with the late Arturo Gatti during their legendary trilogy. They became so close that Ward, who retired after their third fight in 2003, later trained Gatti.

Pacquiao and Erik Morales, who fought three times, also became friends, to the point that Morales even traveled to Pacquiao's home country of the Philippines to shoot a beer commercial with him -- then party with him afterward.

Arum has seen fighters go both ways. He saw the good of the friendship forged between Sugar Ray Robinson and Jake LaMotta, who famously fought six times, and the bad of the sour relationship between Muhammad Ali and Joe Frazier, whose trilogy is perhaps boxing's most famous.

"[A friendship] never quite happened with Ali and Frazier because of a resentment on Frazier's part," said Arum, who promoted more than 20 Ali fights. "But generally there was great love and affection between LaMotta and Sugar Ray Robinson. At the time I was promoting the [Marvin] Hagler-[Thomas] Hearns fight, Jake was getting married again at the Barbary Coast [in Las Vegas] and they had the wedding ceremony the night before the fight. The best man at the wedding was Ray Robinson.

"I asked Jake later why he was the best man at the wedding and he said, 'No, [Robinson] is the best man. He beat me five out of six times.' They just had a great love for each other."