Oftentimes, fans can look at passing game as a receiver "beating" a corner in coverage, and/or a corner "shutting down" a receiver. Most of the time, the structure of the offense or of the defense is what determines success in the passing game. Moreover, the ability to execute within that structure is what is especially vital. There is not a perfect coverage. If there was, every defense would run it, and they would run it every play. Offensive route combination can always beat a coverage. There are cover 2 beaters, cover 4 beaters, cover 3 beaters, etc. Also, teams will run different route combinations on different sides of the formations. So, they can run a zone beater to one side, and a man beater to the other side (remember this next time someone tries to tell you that it doesn't matter if a team has advance knowledge of what another team is doing), and the quarterback will base his first read off of what he sees pre-snap. With all of the being said, the great equalizer for defense is the pass push.
In the first example, Ben Roethlisbeger sees 2 safeties deep and the corners playing tight. Thus, he (rightly) presumes that the defense is playing Cover 2. The weakness of Cover 2 is the area of the field between the deep responsibility of the safety and the flat responsibility of the corner.
Here is an example of the structure of the defense defeating the structure of the offense. There is no threat to the flat on the side of Antonio Brown. As a result, the corner can sink on Brown's route and thus make it a much tighter window to complete the pass. A route to the flat would result in the corner not being able to sink on Brown's route.
Notice, however, that even though the defense defends this play well, it is still almost completed. This goes to show that a perfect pass to a sure-handed receiver is almost impossible to defend.
Creative play-design, as we see on the next play, can make the margin of error much larger.
This is a great example of installing a man beater on one side and a zone beater on the other. The bunch formation makes it very difficult to play man. On the other side of the formation, the Steelers run a high-low route combination to take advantage of zone defense. Because the defense has one high safety, they can be playing either man or zone. Once Ben immediately recognizes zone, he snaps his read, recognizes the hook/curl defender react to the flat route, and hits Brown in stride and with timing.
When people talk about a QB playing with the structure of the offense, this is a great example. Ben knows exactly where Brown is going to be as he turns his shoulders and delivers the ball there. He does not have to "look" for Brown and/or look for the hang defender. He is able to anticipate both. Also, Ben's technique is flawless. His technique allows for the ball to be thrown accurately and with velocity. This is a beautiful football play that cannot be fully appreciated when seen live.
This is also a beautiful play, but its beauty comes pre-snap.
One of the oldest sayings in coaching is "whoever has the chalk last wins." A great QB allows a coach to have the chalk last. Here, once Ben realizes the defense, he is able to take advantage of the mismatch. Here, by the way, is the advantage of having Heath Miller as your tight end. You have to keep a run defender (linebacker) in because Heath's ability to block creates an extra gap to defend. However, the linebacker then has to play coverage. It is not a matter of Heath being a speed burner; simply, both he and Ben know where to go. The timing beats the coverage.
Therein lies the advantage of the no huddle. It allows Ben to diagnose the defense and take advantage of either structural or personnel mismatches.