Forget 49ers-Seahawks ... Alabama vs. LSU is an even bigger matchup this weekend for some in Seattle's locker room -- 'cause D.J. Fluker says there's some hilarious wagers going on!!!

D.J. -- an OL who cut his teeth at 'Bama -- tells us he's going to make some bets with LSU alums Al Woods and Ethan Pocic this week that could have some seriously embarrassing ramifications.

"We talking about full-fledged LSU, full-fledged Alabama gear -- somebody's going to wear it," Fluker says. "I'm going to take a picture of it; hopefully we get to post it all on social media!"