CBS cameras caught Lynch raising the middle finger on both hands in the fourth quarter.
Sunday’s game marked Lynch’s regular-season return to the NFL after sitting out the 2016 season in retirement. He unretired after being traded by the Seattle Seahawks to the Raiders in the offseason.
He rushed for 76 yards on 18 carries Sunday, setting the tone for the Raiders with his bruising running style in Oakland’s 26-16 victory.
“We got to see that Marshawn is Marshawn,” Raiders quarterback Derek Carr said. “He’s running through people, and he’s going to make it a pain on them to tackle him. You’ve got to earn it if you’re going to tackle him.”
Lynch also had a 16-yard reception on the right side and nearly had what could have been a 34-yard TD catch one play later when he drifted out and down the left sideline with no one in front of him.
But Carr overthrew the ball, and Lynch did a front-flip somersault.
ESPN’s Paul Gutierrez contributed to this report.