Buffalo Bills wide receiver Zay Jones got into a bizarre naked struggle with his brother who's also in the NFL, which also ended in a bloody mess ... with Zay in handcuffs!

According to TMZ Sports they obtained this video of the crazy fight that went down Monday night in a downtown L.A. apartment building. Zay is stark raving nude while grappling with his brother Cayleb Jones of the Minnesota Vikings.

Zay eventually broke free, and ran into Cayleb's gf's apartment ... you can hear her screaming. We're told at some point, he ran back out of the apartment, entered a public balcony area and smashed his foot through a window.

TMz was told Zay actually tried to squeeze through the hole in the window, but Cayleb restrained him until police arrived, and arrested him for felony vandalism.

Jones was the Bills' 2nd round draft pick last year.
According to law enforcement sources, he's being held in the medical ward of L.A. County Jail.

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