With Ohio State returning to the Northwestern football schedule in a highly-anticipated night game, I naturally thought of Northwestern's last experience hosting Ohio State under the lights, a 33-27 overtime win in 2004. It turns out that Northwestern Highlights has the game highlights, which I couldn't resist watching. One feature of the game that stood out was Northwestern's use of screen passes to move the ball against a more talented opponent. The highlight tape includes several moderately successful screens that moved the chains, but I want to look at two plays in particular: Northwestern's first and second touchdowns, both of which came on screen passes.
The basic principle of a screen is that defenders love to hit quarterbacks. This means that the offense can rely on pass rushers running right past offensive linemen who let them, freeing the linemen to set up a convoy for a receiver as long as the quarterback can throw the ball before the unblocked rushers arrive. Northwestern put this on display on their first touchdown, a screen to running back Noah Herron.
When Northwestern snaps the ball, the middle of the line allows the defensive line to penetrate and heads left to block. Meanwhile, the lone receiver to that side blocks inside, trying to seal the linebacker.
The key to the play is in that box: OSU has all 4 defensive linemen behind the play, where Northwestern has only quarterback Brett Basanez and two offensive linemen. Defenses always have an unblockable defender (the ballcarrier's counterpart); Northwestern has managed to put that defender behind the ball, moving in the wrong direction. Basanez gets Herron the ball with blockers in front.
Sometimes screen blockers don't make contact; that isn't a problem on this play. Notice that one of the blockers, finding nobody in front of him, has turned back to cut off pursuit. I'm inclined to think that the offense is in better shape if he continues downfield, but I don't know whether Randy Walker would have agreed, and that guy knew a lot more about football than I do.
Herron has an easy chance to make a man miss and walks in for the touchdown.
Later in the game, Northwestern comes out in trips again.
The Ohio State defense is shaded to the offensive right, which will turn out poorly for them. At the snap, Basanez rolls right with Herron leading; the linebackers follow them. Mark Philmore, all alone on the left, jabs downfield before looking for a pass, while the offensive line releases to the left.
Once again, Ohio State has too many men in the backfield, with three defensive linemen facing down Brett Basanez and a single offensive lineman. The linebackers, meanwhile, have both run themselves out of the play to the right in an attempt to contain Basanez and Herron.
On this receiver screen, the left tackle (I think it is Zach Strief) has an extremely tough assignment. He has to sprint outside, locate the corner, and prevent him from disrupting the play. The block here is a bit dodgy and could reasonably have been flagged as a block in the back, but it does the job. The throw stretches Philmore out, but with the tackle hitting the corner he has plenty of room to work.
Ohio State is in awful position once the catch is made. Presnap, they only had two defenders outside the hashmark: a defensive end (now watching the play from well behind) and a cornerback (now watching the play from underneath an offensive tackle). Two defenders manage to get in the right neighborhood, but they are easily blocked by the screen blockers. A third catches up as Philmore dives into the endzone to extend Northwestern's lead.
When well executed, screen passes look like the easiest plays in football. In reality, there is a lot that can go wrong. They require precise timing between the components of the play; if the quarterback holds the ball too long, he will actually get hit or the defense will read the play and camp out by the receiver. If the linemen don't arrive with the ball, there will be no screen of blockers for the receiver. An Ohio State screen from the same game shows what can happen when the timing is a bit off.
Facing third and long, Ohio State wants to take advantage of an aggressive pass rush by throwing a receiver screen. They line up with an empty backfield, with three wide receivers to the right and a tight end left.
The Northwestern pass rush does get drawn upfield, but OSU's linemen are slow to get outside. When Josh Zwick releases the ball, a Northwestern defender has read the screen and is heading, unblocked, for Santonio Holmes.
By the time Holmes has secured the ball, he is being tackled. Because he is Santonio Holmes playing against a Northwestern defense, the first attempt doesn't bring him down. It does, however, prevent him from turning upfield and buy time for the rest of the defense to rally to the ball. Holmes is forced to head outside, where the defense traps him against the sideline.
As Holmes fights for yardage, he fumbles, though he is able to quickly recover the ball and set up a punt.
In the example above, a good read by the first Northwestern defender was aided by poor timing from OSU's offense. One final example, from the Gator Bowl against Mississippi State, shows another way to stop screen passes.
Like Ohio State in 2004, Mississippi State wants to take advantage of a defense coming at the quarterback on third and long. The play is essentially the same as Northwestern's first touchdown from the 2004 game: a running back screen to the single receiver side of trips.
As the blockers head outside, however, there is already a problem: only three defensive linemen have taken the invitation to rush Tyler Russell. Instead of rushing upfield, Tyler Scott has read the screen and is accompanying the blockers outside. Additionally, the single receiver, facing a cornerback playing press coverage, must draw the corner downfield instead of sealing a linebacker inside. With the offensive tackles staying inside, the offense has failed to generate a numerical advantage.
The play might still work, as Northwestern's free defender is the free safety. As the catch is made, however, it becomes clear the the defense has won this time. Scott drives his inside shoulder into a blocker, setting up to either force the running back inside or to make the tackle if the back goes outside. David Nwabuisi, meanwhile, avoids an attempted cut block from another blocker; if the back heads inside, Nwabuisi and the pursuing defensive linemen should make the tackle. As it happens, Scott is able to make the tackle and bring up fourth down.
At their core, screen passes are misdirection plays. Like most such plays, the offense's execution must be precise to sell the fake. Even when the offense does everything right, a single defender who makes the right read can negate the offense's advantage. This limits the frequency with which an offense can throw screens successfully; at a certain point, the defense won't respond to the unprotected quarterback. As a simple way to neutralize an opposing pass rush that might be overly aggressive or simply too talented to block effectively, however, they are an important part of a pass offense. For teams with talented open-field runners, they provide the additional benefit of giving a player the chance to make a play with the ball in his hands.