The beating after Thursday’s season opener between the Giants and Los Angeles Dodgers left the victim in critical but stable condition.

Investigators were also checking to see if any security camera captured the attack, but Detective Larry Burcher said so far they’d found "nothing of great value."

"We’re very confident there were witnesses, it happened immediately following the game when everybody was coming out," Burcher said.

Police said the two men, who were wearing Dodgers clothing, began taunting three men in Giants gear with expletives as thousands of baseball fans left the stadium after Thursday night’s 2-1 Dodger victory, Detective T.J. Moore said.

The Giants fans tried to distance themselves from their assailants, and two made it away from them, but one was struck with fists on the back of the head and as he fell, his head hit the ground in Parking Lot 2 on the third base side of the ballpark, Moore said.

Both attackers then kicked the victim, who suffered a head injury, and ran, Moore said. The suspects fled in a four-door sedan driven by a woman with a male child passenger in the vehicle, Moore said.

When the victim’s friends turned around to look for him, they saw him on the ground and made their way back to him.

Police paramedics on bicycles were the first to arrive to help the victim. An ambulance was called and the victim was taken to a nearby hospital, Moore said.

The victim’s name wasn’t released, but KGO radio in San Francisco and the Santa Cruz Sentinel identified him as Bryan Stow, a 42-year-old paramedic from Santa Cruz. His brother-in-law, David Collins, told KGO that Stow, a father of two, has severe head injuries.

"It’s sad," Giants manager Bruce Bochy said before Friday’s game against the Dodgers. "It’s a shame somebody’s in critical condition because of a ball game. When they’re out fighting in the parking lot, we’ve lost sight of what this is all about. Sounds like the guy got blindsided, too."

The Dodgers said they were co-operating with investigators and wished the victim a speedy recovery.

"It is extremely unfortunate that this incident took place on what was otherwise a great day at Dodger Stadium for tens of thousands of fans," the team said in a statement. "We’re committed to having the most fan and family friendly environment in baseball and will continue to make that a top priority."

The stadium has been plagued by opening day violence in the past.

In April 2009, a man stabbed his friend in the stadium parking lot after the home opener, in which the Dodgers. Arthur Alvarez said he acted in self-defense and was acquitted by a jury.

The West Coast rivalry began on April 18, 1958, the first game played in California after both teams had moved from New York. The Dodgers beat the Giants 6-5 in a game played before nearly 79,000 fans at the Los Angeles Memorial Coliseum.

"I was disappointed," new Dodgers manager Don Mattingly said about the Thursday attack. "You don’t want to see that. Everyone likes rivalries, but to me that’s crossing the line."