Enough.
New England had two guys playing tackle that had no business being out there. They were matched up against DeMarcus Ware and Von Miller, two plays who were already matchup nightmares, but had the benefit of knowing the silent snap count down to a millisecond. Those two guys were in the backfield before either Cannon or what's-his-face even got out of their stances.
But you're right, D-Lineman should never drop into coverage, only blitz. That's how Von Miler got his pick, after all.