LAS VEGAS

Hours after one punch drastically changed the boxing landscape, Bob Arum retired to the showy Nobhill Tavern at the MGM Grand for a late birthday celebration. He turned 81 on Saturday, and he moved among the tables with a vodka and soda in his hand.

“Age doesn’t matter!” he kept saying. “Look at me!”

Arum continued like this, about boxing, about Mitt Romney, about a fight as savage and thrilling and conclusive as they come. The winner, Juan Manuel Marquez had sung “Happy Birthday” to Arum at the post-fight news conference, with a concussion and a broken nose. The loser, Manny Pacquiao, sat in a nearby hospital, having a brain scan.

Someone like Arum, the chairman of Top Rank Boxing, does not survive decades in this sport without an instantaneous ability to adapt. Where some saw a near-certain decline in Pacquiao-related sponsorships and advertising dollars, and where others saw a Marquez victory darkened by drug allegations that Marquez and his camp vociferously denied, Arum saw opportunity. Of course he did.

“What a fight!” he said.

As guests ate strip steaks and lobster claws in cream sauce, Arum’s mind spun forward. Before Saturday, all the Pacquiao-Marquez trilogy had produced was consternation and confusion. Well, that and a lot of money for those involved. The first three fights ended with debatable conclusions, with no clear winner, except for Pacquiao on the scorecards, twice.