Two men started fighting after the game and it doesn't appear the fight had anything to do with a sports rivalry, San Diego police Officer David Stafford said.
The injury doesn't appear to be life-threatening, Stafford said. The victim was treated at a hospital for a stab wound to the abdomen.
Stafford said there is no suspect description at this time. He said the victim was uncooperative with police.
The stabbing is the second violent incident after a Raiders' game this season. On Aug. 20 following San Francisco's exhibition victory over the Raiders, two men were shot in the Candlestick Park parking lot.
A 24-year-old man, who reportedly was wearing a "F--- the Niners" T-shirt, was hospitalized in serious condition after being shot several times in the stomach. A second victim, a 20-year-old man, was treated for less serious wounds in a separate shooting.
Those attacks came nearly five months after San Francisco Giants fan Bryan Stow was severely beaten by two men in Los Angeles Dodgers gear outside Dodger Stadium after the archrivals' season opener in Los Angeles. Two men charged in the beating, Louie Sanchez and Marvin Norwood, have pleaded not guilty.
Stow, a Santa Cruz paramedic, sustained severe brain injuries and remains hospitalized in serious condition.