On this play, Merling made the pick 6. It was amusing because he and Crowder were talking about it on Saturday night, and he said he had never touched the ball since high school, and here was a perfect pass right to him.
Miami lined up with 4 down linemen, 3 linebackers, and in a zone against the three wide formation. Merling's assignment was to cover the running back, if he went to the right side of the offense. He's lined up left, of course, you're pass rushing, and you're a rookie. It would be easy to forget that assignment.
But Merling did not. If you look at the second shot, you'll see that Merling broke off his rush and fell into coverage. Now, I wouldn't say the coverage was all that great, but Favre tried to force it in there, and Merling simply grabbed it out of the air and started running. He made Favre sit down, and drove into the endzone.
He was opportunistic, but followed his assignment and was highly successful. AND, we have to mention that Favre threw a not-too-great pass.
I have to assume that there was some scouting on this formation to be ready for it as well. Kudos to him and Pasqualloni.