Some rivalries just build up quickly, but others slowly bubble up to the surface from the most unlikely of places possible... teammates. Whether it's teams like Colby Covington vs Dustin Poirier and Tj Dillashaw vs Urijah Faber or Frank Shamrock vs his brother Ken Shamrock... these are about as bitter as it gets. But for some reason the fights never happened. Why not? We'll break that down in today's video.