He fails miserably. This is directly after the snap. The defender whiffed on his ham, and is already behind McCoy (defender is circled in red). McCoy is free to run his route: a skinny-post to the end zone. From this shot, you can already pretty much see how easily he'll be able to split the defenders.
The defender is hopelessly trying to catch up to the streaking McCoy. The Cowboys appear to be in zone, but there's a mix-up somewhere. Between the original defender (red circle) and McCoy (white circle), there's a Cowboy's defender who appears to be covering no one. I'm pretty sure he was supposed to pick up McCoy here. The single-high safety is moving in the other direction for no apparent reason. Sure, there's a receiver on that side, but he's being covered pretty well (the CB has inside technique and has the receiver pinned to the sideline), and the safety would have no shot of making it over there if the throw went that direction, anyway. His attention would've been better spent shading the way of McCoy, since there are three receivers on that side of the field.
In this shot, the ball is in the air, the safety is too late in reacting, and all McCoy has to do is catch a perfect ball for a touchdown. Which he does.
I have two favorite things about this shot:
1. There are two Cowboys defenders in the red circle. The one is still hopelessly pursuing McCoy, while the other got turned around in trying to pick up McCoy late. The second defender never covered anyone.
2. Even if McCoy wasn't wide open, there is a Seahawks receiver wide open in the middle of the field (at the 21) with plenty of room to run. Had Wilson just dumped the ball off here, it would've been a pretty good gain (and, depending on how good the downfield blocking by the receivers was, he would've had a decent chance for a touchdown).
As it was, Wilson read it wonderfully and threw a perfect strike to McCoy.