Cam Newton's Ex-Teammate Confident QB Isn't Done, 'More Left In The Tank'

Cam Newton's NFL days are NOT numbered ... so says his former teammate Trai Turner, who tells TMZ Sports he believes the quarterback "has more left in the tank."

Newton is coming off his worst season as a pro -- throwing just eight touchdown passes to 10 interceptions -- and it's got some wondering, is retirement the next move for the former NFL MVP?

Turner -- who blocked for Cam from 2014 through 2019 in Carolina -- says hell no ... telling us people shouldn't rush to judge Newton's future based off his 1 year in New England.

"First year on a new team and it's just different man," Turner says. "Different people around you. Different city, new place and all that. But, I don't think that was the last showing that Cam would have wanted."

"Me just knowing him and knowing what he can do and just being able to see him play, I know that he has more left in in the tank to give."

Newton is slated to be a free agent this offseason ... and he's already promised to come back to the league next season a better player.