After his team's big win, the Niners cornerback claimed Mayfield refused to shake his hand prior to the coin toss.
"What's amazing, and annoying, was him not shaking hands at the beginning," Sherman said, according to NFL.com's Mike Silver. "That's some college shit. It's ridiculous. We're all trying to get psyched up, but shaking hands with your opponent - that's NFL etiquette.
"And when you pull bush-league stuff, that's disrespectful to the game. And believe me, that's gonna get us fired up."
Sherman responded by intercepting Mayfield's fourth pass of the contest. Overall, the entire Niners defense got after the sophomore pivot, registering eight quarterback hits and four sacks. Mayfield was limited to 8-for-22 passing for 100 yards, two interceptions, and no touchdowns.
Afterward, Sherman also implored the 24-year-old quarterback to "respect the game."
"He hasn't earned anything in this league. How many games has he won? He's acting like he was the MVP last year," the cornerback said of Mayfield. "If (Patrick) Mahomes did that, it would be one thing. But he would never do that, because he has too much respect for the game. And when you see a guy who doesn't? You humble him every chance you get. Because eventually, he will have respect for the league - or he'll be out of it."
San Francisco defensive tackle DeForest Buckner also said Mayfield snubbed his team before the game, while tight end George Kittle said he earned just a quick handslap.
"Everyone has their own alter ego that they lock into. His is, 'I'm going to mess you up.' I don't mind it. He's gone a long way with it," Kittle said.