The angry letter is addressed to Barton at La Commanderie, the training ground of French side Olympique de Marseille, where the player spent a year on loan.
The writer appears to struggle with the English language as much as Barton did at the time, making very little sense as he threatens to "smash your head shots baseball bat".
The "fan mail" also warns Barton that he'll "die a knife open mouth since emptied your blood".
As if the grammar and choice of words wasn't odd enough, writer Cvetko Ivanovic signed the letter and included a return address, as if expecting further correspondence.
Barton seems to have waited until he was safely back in the UK to share the picture, after completing his 2012/2013 stint in France.
The QPR star took the threat in stride though, channeling the famous Wealdstone Raider in his response.
Barton did end up playing his last game for Marseille before Ivanovic's ultimatum, as he landed a two match suspension for calling Thiago Silva an "overweight ladyboy".