Originally I had thought Buffalo played this with Cover 6, which is essentially Cover 4 to the top of the screen (twins side) and Cover 2 on the bottom. But it's difficult to say. This could be Cover 3, it could Cover 0 with two drops underneath. Regardless, this is a play that was designed to attack both 2-high safeties and single high defenses, and at this point it seemed that Buffalo had begun running more 2-high looks to prevent the big plays. But a play shouldn't just work against a single kind of defense, and I'll try to explain why it worked so simply here as against this defense as well. What's interesting about this play is that it isn't originally a spread concept. I actually stems from many other offenses. In the West Coast Offense it's a scissor concept. You'll see it in run and shoot and other offenses as well. So both of these pass concepts are borrowed, but with the run threat provided by the spread, it becomes easier to read and predict the defenses.