Richard Sherman Guarantees Dominance Over Marshawn Lynch in New Football League

Richard Sherman is taking his role in the Fan Controlled Football League VERY seriously ... telling TMZ Sports he's GUARANTEEING win after win against his good friend, Marshawn Lynch.

Sherman and Lynch just signed on to be owners and captains in the FCFL ... a football league where the fans decide everything from the roster, the team name, logo and even the play-calling.

Although the 49ers star says he won't be suiting up for the FCFL after his playing days, he makes it clear he is out for blood when his team goes against Beast Mode's squad.

"It's gonna be really fun. Obviously, we're gonna have to beat his team over and over and over again," Sherman says. "I hope he doesn't get too upset at that."

There's a silver lining for Lynch, though ...