KSI's boxing return has hit a snag ... his opponent, Wayne Bridge, pulled out of their planned March tilt just hours after it was initially announced -- and it's all due to some pre-fight trash talk.
The retired soccer player announced his decision to step away from the match on Monday morning ... saying the comments KSI made over the weekend about an alleged affair involving his ex-girlfriend and his former teammate "crossed a line."
The controversial words came on Saturday .