He reportedly waited for the cyclist at a petrol station and threatened him with the firearm.Suzy, 26, regularly posts pictures on social media of her showing off her posterior while draped in a Messi shirt - antics which she believes has caused her to fall foul of Messi's wife, Antonella Roccuzzo.
Matias Messi, 35, was detained in a hospital in Rosario, northern Argentina, where is recovering from a fractured jaw and other injuries sustained from what he claimed was a boating accident.
Cristiano Ronaldo was crowned the best male footballer in the world for the second year running, fighting off Lionel Messi and Neymar to scoop the top prize.
The Puskas Award for the best goal of the year was given to Arsenal striker Olivier Giroud's stunning scorpion kick against Crystal Palace, whilst Zinedine Zidane easily saw off Antonio Conte and Massimiliano Allegri to pick up the trophy for Best Male Coach after his Champions League/La Liga double.
He claimed he had been navigating the boat alone when it had crashed after hitting a sandbank.
The villager reportedly wrapped him in a sleeping bag and piloted the boat to a nearby fishing club where Matias was rescued and taken to Rosario's Parque sanitarium hospital.
Suzy, from Distrito Federal, Brazil, unveiled her campaign on Instagram last week, writing: 'I am a fan of @fcbarcelona and a big fan of @leomessi guys help me launch the campaign with the hashtag #Un Block Me Messi.
Thanks friends.'Speaking of the alleged blocking, Suzy told Mail Online: 'Much of this has to do with his girlfriend, Antonella Roccuzzo who has, rather unsurprisingly not taken well to the idea of a model sending her partner x-rated posterior pics.'Suzy, who is known in her home country for dating soccer players, scooped the highly-coveted Miss Bumbum 2015 title last November after battling it out in front of 15 other South American beauties in Sao Paulo.
Matias said he fractured his jaw and nose after hitting a sandbank while driving a speedboat on the Panama River.
But police investigating the incident found an unregistered 380-calibre pistol on the boat he was piloting, which had 'numerous blood stains', according to the prosecutor who ordered his arrest.
This isn't the first time Matias, who is five years older than his famous brother, has had brushes with the law for allegedly illegally carrying a firearm.
The Barcelona star's brother, who has been linked with known criminals in the past, was held for 16 hours in a prison cell for in 2015 after officers found an an unlicensed.22-caliber gun in his car.
He was also ordered to stay off drugs and drink and pay a fine of around €470 (£415).