"I think he may surprise some people," No. 4 says.

A lot of football pundits disagree ... saying it's only a matter of games before Jones -- the Giants' first-round pick this offseason -- gets the keys to the car.

But, Favre is confident Eli will play well enough to keep his job ... and is saying the QB has the perfect mentality to have a huge 2019 season in New York.

"I think he'll have a better year than most are giving him a chance to have."

Favre tells us it's the Giants' system that gives him confidence in Eli, saying, "He's got some really great, young, talented players around him, and he knows he doesn't have to do too much."

The Giants kick off the season Sunday afternoon against the Dallas Cowboys ... can he prove Favre right??