Oh a mouse happen to walk by, that's how Blue got defeated. That's, kinda lame but I suppose I can at least credit it for being totally in-character. I suppose Blue's personality has been built up more than him as fighter, so it's fitting that'd he lose to something like that. Just a bit disappointing.
Though all that disappointment left me once Goku actively searched for the mouse, deciding to save it's life, and then stuff it in his mouth. That's just so sweet.