Warren Moon is the only player in the CFL and the Pro Football Hall of Fame -- so, if Johnny Manziel is gonna make it in Canada, there's NO ONE BETTER to listen to than this guy.
TMZ Sports spoke with the 61-year-old legend, who truly believes Manziel can thrive up north and earn his 2nd shot in the NFL ... IF he takes Warren's advice.
But the bigger point ... Moon believes even if Johnny doesn't get back to the NFL, he can have a very long and successful career in Canada, because the game is uniquely suited for him.
Bottom line ... TAKE THIS MAN'S ADVICE -- he knows what he's talking about.