Julio Jones Is 'Definitely a Hall of Famer' ... Says NFL Legend Mike Haynes (VIDEO)

Get the bust ready in Canton, because Julio Jones has ALREADY earned a spot in the Pro Football Hall of Fame ... so says someone who's already there, Hall of Famer Mike Haynes.

The Raiders legend has touched down in Houston where he's already singing Julio's praises -- saying the ATL Falcons stud is "one of the premiere receivers of all time."

FYI, Jones is only 27 ... he's a 4-time Pro Bowler, led the league in receiving yards in 2015 and set the Falcons single game yards record with 300 in one game.

Dude's a beast ... but does Haynes think HE coulda stopped Julio back in his prime? We asked.