San Francisco police said Michael Montgomery, 21, was arrested on suspicion of homicide. Another person, whose name was not released, was also taken into custody.
"One of the suspects during the course of the interviews (with detectives) made incriminating statements that give us the indication that he will be the person booked for homicide," Police Chief Greg Suhr told reporters.
"We're trying to figure out what we're going to do with the other suspect," Suhr continued. "The investigation is still ongoing."
The altercation several blocks from the ballpark was the second violent confrontation between Dodgers and Giants fans in the past several years to end in death or serious injury. Bryan Stow, a Northern California paramedic and Giants fan suffered a traumatic brain injury after two men dressed in Dodgers gear attacked him following the teams' March 31, 2011, game in Los Angeles.
Stow's family said in a statement that they were "horrified and deeply saddened" by Wednesday's violence. "Our thoughts and prayers go out to the family."
Two Dodgers fans are awaiting trial on charges in the beating, which sparked outrage and brought stadium security changes around the state and country.
Denver, his father and his brother had left a bar around 11:30 p.m. about 90 minutes after the game ended when they exchanged heated words about the Giants-Dodgers rivalry with another group of people leaving a nightclub.
One of the members of the group was wearing a Giants hat, Suhr said.
A fight broke out, and no one was seriously hurt at first. But a second altercation occurred a few minutes later, Suhr said.
"We're not sure at this time who wouldn't let it go. It wasn't clear who started the second fight," Suhr said, but it ended with Denver's stabbing.
Police were canvassing the area Thursday looking for the weapon used to kill Denver and any surveillance video of the crime.
Violence has marred previous contests between the teams. In 2003, Giants fan Marc Antenorcruz, 25, was fatally shot by a group of Dodgers fans after a drunken argument at Dodger Stadium.
___
Contributing to this report were Associated Press writers Lisa Leff, Jason Dearen and Haven Daley, and Sports Writer Janie McCauley in San Francisco; AP Sports Writer Beth Harris in Los Angeles; and researcher Rhonda Shafner in New York.