Interceptions- Where Are They Thrown?

I've been racking my brain trying to find a pattern as to where intercepted passes are most commonly thrown. Are they more often thrown to one side of the field as opposed to the other, more often down the middle, to the sidelines? A lot of questions, all meant to identify if a quarterback's target and location patterns could tell us more about why he throws so many interceptions.

My first theory: Quarterbacks who throw far more towards one side of the field than to the other become predictable, and thus, intercepted more often.

To examine this theory, I looked at the 2007 statistics of all quarterbacks and broke up the distribution of their pass attempts. Luckily, ESPN.com provides a breakdown of left sideline, left, right sideline, right, and middle. More frequently intercepted quarterbacks should have a more lopsided distribution from one side to the other. However, nothing really came of this. Regardless of whether the quarterback is extremely lopsided or even-handed to both sides of the field, the equity of distribution has no relationship to his interception rate.

For the record, the most even handed QB's are:
Philip Rivers, Drew Brees, Peyton Manning, Carson Palmer, Derek Anderson.
and, in case you're interested, the guys with a favorite side are:
Matt Hasselbeck (23% more to the right), Brett Favre (19% more to the right), Rex Grossman and Marc Bulger (18% each more to the right), and Tarvaris Jackson (13% more to the right).

My second theory: QB's who throw more passes to the middle of the field will be picked off less.

A QB who throws to the middle of the field will theoretically force the defensive backs away from playing only to one side and will require them to spread out. Furthermore, a quarterback who throws a lot to the middle likely has great confidence (either in himself or in his receivers), as opposed to a quarterback who dumps off or throws to the side a lot.

This theory yielded mild support. There is a significant, albeit modest relationship between the percentage of times a QB throws over the middle and the amount of times he's intercepted. Those who do it more often are actually picked off less, although the difference is not tremendous.

The five biggest up-the-middle gunslingers:
Brett Favre (19%), Jeff Garcia (17%), Kyle Boller (17%), Drew Brees (16%), Damon Huard (16%)

The five who rarely go up the middle:

Rex Grossman (9%), Carson Palmer (9%), Tarvaris Jackson (10%), Jason Campbell (10%), Marc Bulger (10%)

My third theory: QB's who throw more to the sidelines are more likely to get picked off.

This theory was more what researchers call an exploratory research question, or less euphemistically, a hunch only modestly based on evidence. I figured, hey, maybe if those who go up the middle are picked off less, those who go straight for the sidelines are picked off more. Remember, there are other areas aside from up the middle and the sideline. The sideline is the three-yard area near the sideline. The middle is inside the hashmarks. so, anywhere outside that range qualifies as left non-sideline or right non-sideline.

Anyway, this theory came up empty. There is no relationship between the percentage of sideline passes and interception rate.



Finally, I started thinking...I'm still sold on the idea that predictability will lead to higher interception rate. But it seems that interceptions have no relationship to how predictable a QB is related to where he'll throw the ball to. That begged the question- What if a QB is predicatble about who he throws the ball to?

Whether a receiver is lined up in the slot, wide right, wide left, some QB's simply have a favorite target, regardless of where he is lined up. Sometimes, though, the quarterback likes the target so much, that the defense can anticipate the two hooking up, leading to higher interception rates.

Eureka!

Final theory: The higher proportion of passes going to the team's leading receiver, the higher that quarterback's interception rate will be.

This theory checks out. There is a robust 0.36 correlation between the percentage of passes thrown to a team's leading receiver and the quarterback's interception rate.

Last year, four receivers were thrown more than 30% of their team's passes. Those men were Baltimore's Derrick Mason, Cincy's TJ Houshmandzadeh, Denver's Brandon Marshall, and KC's Tony Gonzalez. The QB's on three of those teams were veritable pick machines, with Kyle Boller, Carson Palmer, and Damon Huard each having an interception rate of over 3.5%, which is very high.

So, it appears that an over-reliance on a favorite target is a large hindrance to an offense. This should be kept in mind when evaluating how good a QB is at spreading around the ball, and thus, the defense.