Deshaun Watson's big question to Jilly Anais earlier this month could be a big boon for the Cleveland Browns -- and the quarterback's wallet -- 'cause Nate Burleson tells TMZ Sports he could see the engagement sparking some improved play ... and more endorsement deals.

The 29-year-old signal-caller proposed to his longtime girlfriend over the weekend ... and now that the two are promised to wed, Burleson told us out in New York City he could see Watson's game all the sudden turning around.

"I think finding a woman and locking in the right spouse can work wonders for him as an athlete," Burleson said. "I wouldn't be surprised if Deshaun Watson plays his best football that we've seen in a long time. Having stability at home provides a solid foundation on the football field, in my opinion."

A 180 from Watson would sure be appreciated by Browns fans ... as he's been a big disappointment since coming over in 2022 from Houston.

Despite being paid $230 million, he's played in just 17 games ... and has been mired in off-the-field controversies as well.

Burleson, though, says he could see a big rebound -- even away from the gridiron.

"I do feel like if he gets married," the ex-NFL star said, "and wants to lock in some endorsements and partnerships with bigger brands, they might look at him a little bit differently."