Chill, that ain't coming from us ... those are the sentiments of HOF signal caller Warren Moon, who's adamant, bringing TB12 to Big D is the wrong move.

Remember, during a recent radio interview, T.O. said Jerry Jones should sign Brady -- a free agent -- and hand him the starting job.

But, Moon tells TMZ Sports he ain't down with Owens' plan.

"I don't think it's a bad idea for anybody to sign Tom Brady cause I think he can still play, but I just don't think it's a good fit for the Cowboys right now because of the way that Dak Prescott has developed, and he's only gonna get better," WM tells us.

The Cowboys had a disappointing season as a team -- they missed the playoffs -- but Dak put up big numbers ... throwing for over 4,900 yards with 30 TD's and only 11 picks.

Prescott's stats -- with the exception of 3 less interceptions -- were significantly better than Brady's ... and according to Warren, that's not some fluke ... DP's numbers were better 'cause he's a better QB.

"[Dak] definitely played physically better than Tom," Moon says.

"Tom still has those mental gifts that you can't compare because he's got so much experience behind him, and he knows how to play in the biggest games, and that's something you gain when you bring in a Tom Brady."

"But, physically, Dak can really throw the football. He knows how to spread it around. He can run the ball and use his legs. So, I think physically he's a better quarterback than Tom right now."