Drake is furious that Chris Brown has used him as a scapegoat in his breakup with Karrueche Tran ...
deflecting his own responsibility by suggesting she was his side piece.
Brown re-ignited his feud with Drake by Instagraming Saturday that Drake secretly dated Karrueche earlier this year while Chris rotted away in a jail cell.
Sources connected with Drake say there's no truth to the dating allegation ... he says Karrueche isn't even his type.
As one source puts it, "Drake's an ass man. Think about it, all the strippers he gets with ... the first out of his type was Rihanna."
Drake acknowledges he hung out with Karrueche in Toronto ... but only because she was friends with a girl who he was hooking up with.
Karrueche has jumped into the fray ... claiming Chris repeatedly "mistreated" her. Given the Rihanna backdrop, that word is loaded.