Passing the ball in college football involves a complex game of cat and mouse between offensive and defensive coordinators, and between QB's and wide receivers and their defensive counter parts.
Before a pass play is even chosen, offensive coordinators will consider a variety of variables. They will check, or at least think about, a running play list while considering such things as field position, momentum and who has it, how the team is blocking along the OL and with the backs, what kind of defense they expect to see in terms of both alignment and personnel, and other variables.
A play will be sent in.
Each play will typically involve a formation and base play call. The base play call will allow a variety of possible calls depending on the defensive formation, and those calls will then typically be made at the line of scrimmage by the Penn State quarterback.
Some fans have posted on the internet from time to time that they believe the Penn State QB does not, or is not allowed to, audible at the line of scrimmage. This is far from the case unless in certain specific situations the staff calls for a specific play to be run regardless of defensive alignment. But that isn't the norm these days.
Many teams we play use a what is called a Cover2 base defensive set with their defensive backs. Penn State uses this formation, our opponents use it, and most of the NFL teams use it as their base package these days.
A Cover2 is a defensive set where you have a defensive back covering each WR in man to man coverage near the line of scrimmage and for a set number of yards downfield, and where there are two deep safeties in zone coverage support.
In a standard Cover2 you'd have two corners playing two wide outs in man to man with two deep safeties in support. In a nickel package you go to three d-backs, the two corners, a nickel back who is typically lined up in the slot, and the two deep safeties.
Below I have two diagrams. In the first I will show you a play call that came with about 5 minutes left in the 3rd quarter against Michigan. It involves a 3rd and long situation (10 yards) for which Michigan predictably brought in a nickel package and Penn State predictably went to a 3 WR set.
Prior to the snap, Mills came to the line of scrimmage to see each WR covered very tight at the line of scrimmage, two safeties playing a deep zone roughly 15 yards downfield, 3 down linemen, and 3 linebackers. The middle linebacker (m) is showing blitz all the way before the snap and is lined up virtually in the 0 gap to the right of the center.
Michigan would, in fact, rush all three linebackers on the play. Their D Coordinator would rightly expect Larry Johnson (B) to stay in to help block on such a blitz package, which he did. The arrows coming from the linebackers all show the direction and gap where they blitz on the play.
Mills is in a shot gun and there is no real ball fake on the play. Instead, Penn State uses the routes run by the receivers to pull the safeties one way or another. Tony Johnson is split wide left and runs a stop curl route just beyond the first down marker. The safety on his side is supposed to read the movement of the TE first, and since the TE stays in to block the safety then looks to Tony and is pulled one or two steps to his side before realizing the play is going to go to the other side of the field. That safety then rotates over to his left (the right side of our offense) to help out on the play but is never in a position to stop the pass. He is only available to help tackle the WR if the pass is completed.
Bryant Johnson is split out very wide to the right and he runs a fade pattern 25 to 30 yards downfield. Gerald Smith is in the slot and runs a short post in the 15 to 18 yard range.
At the snap, the safety on the right side of our offense must make a decision to either help cover on the fade route or help cover on the post route. Most of the time a safety will cover the post since the corner has the sideline to help him. But on this play, if you closely examine the diagrams you might notice that Michigan has lined the nickel and corner up to the inside of both receivers in an effort to force the play to the outside. When Smith and Johnson both come off to that side is causes the safety to initially break to the outside, the direction Michigan wants to the play to go to in the first place.
The key on this play for Michigan is that they are in an all out blitz. They are trying to force Mills to throw quickly. They would also like to jam the WR's right at the line of scrimmage. The blitz will have to be picked up by the PSU offensive line with the help of Larry Johnson in the backfield. The line wipes out the middle backer and the weak side backer on the play and Larry Johnson blocks the strong side backer successfully.
The key for Penn State is that both receivers get off cleanly at the snap. If either is successfully jammed at the line of scrimmage, the safety can proceed instantly towards the other target.
Mills is in the shotgun and is going to read the movement of the safety and the movement of the two receivers. At the snap, the safety on that side initially takes a step or two to the outside before shading back to the inside to help with the post pattern. As noted, a key to the play is that Gerald Smith gets off cleanly, which he does on the play.
Mills knows that once Smith has gotten off cleanly it becomes almost impossible for the nickel back to cover him so close that the nickel would be in position to break up the pass. The throw has to be made prior to the break and will get there at a point in time just prior to the nickel being able to catch up the the play and defend it if thrown on time and on target.
Once Mills has read the initial outside movement of the safety and the clean break by Smith, the flanker becomes the intended target and Mills throws the short post to Smith. Both safeties read the throw (noted with a dashed line) and rotate back to the play, but they arrive after the ball is caught and only in time to assist with the tackle.
Here is a diagram of the play as it is successfully completed for a Penn State first down.
The next play I have diagrammed comes only two plays following the one I diagrammed above. Penn State is facing a 2nd and 8 play from somewhere near their own 35 yard line. Penn State comes out in a Power I formation and Michigan is lined up in the most basic of all defensive alignments, the 4-3 front with a Cover2 pass package.
This is a down and distance situation where the offense will typically throw a short pass or run the ball about 80% to 90% of the time. The Michigan defense has to play with their linebackers reading the movement of the fullback, tight end, and running back. The linebackers will obviously be defending a running play or covering these three players.
When the TE stays in to block the defensive end, the strong side linebacker blitzes to his inside shoulder and is picked up by the right tackle Matt Schmitt.
On the snap, our fullback moves to his left in a short pass route to the flat and drags both the weak side linebacker and the middle linebacker in coverage. This helps Mills know he should have plenty of time to throw the deep pass he is looking for.
After a play action fake to Larry Johnson which further slowed the weak and middle backers, Larry would move in the same direction at the snap as does McHugh. But Larry i