San Francisco police Chief Greg Suhr told reporters Thursday the victim, Jonathan Denver, 24, had left the stadium during the eighth inning with his father, his father's girlfriend, his brother and another friend -- and the group was about 4 blocks from the park when they got into a "back-and-forth about the Giants-Dodgers rivalry, which deteriorated into a physical fight."
The Dodgers said Thursday Denver was the son of a security guard at Dodger Stadium.
Suhr said the fight did not result in serious injuries, but a second fight broke out in which Denver -- who was wearing Dodgers gear -- was stabbed, the Los Angeles Times reported.
Two people in the other group were detained a few blocks away and were questioned Thursday, Suhr said.
Police were asking the public to report whether they had any cellphone video or surveillance video that might help identify Denver's attackers.
Suhr said San Francisco police had deployed what he called a "rivalry package" of enhanced staffing for the baseball game, which was played three days after a teenager was attacked at San Francisco's Candlestick Park while the 49ers were playing the Indianapolis Colts, despite stepped-up security at the football stadium.
The Giants plan to hold a fundraiser this week for Bryan Stow, a Giants fan who sustained traumatic brain injury when he was beaten by two men in Dodgers gear outside Dodger Stadium in Los Angeles on Opening Day 2011.