A Logical Look at What Happened in the Carolina vs Arizona Game

The Carolina Panthers, played in the toughest division in the NFC, the NFC South.  The Arizona Cardinals played in the easiest, the NFC West.  The Panthers completed a 12-4 season.  The Cardinals were 9-7.  The Panthers were 8-0 at home.  The Cardinals were 3-5 on the road.  The oddsmakers in Vegas decided that this was good enough to favor the Panthers by 9.5 to 10.0 points.

Result - Arizona beats Carolina 33-13

What Happened?

Jake Delhomme threw a career-high 5 INTs.  That was unexpected.  A shocker.  But, how unexpected was it, really?

Let's take a look at some #s.

First, what are the chances of winning a playoff game, when a QB throws X interceptions?  Here are the stats:

0 INTs - 184-51, a winning percentage of 0.783

1 INT - 140-112, a winning percentage of 0.556

2 INTs - 54-117, a winning percentage of 0.314

3 INTs - 17-76, a winning percentage of 0.183

4 INTs - 1-27, a winning percentage of 0.036

5 INTs - 0-11, a winning percentage of 0.000

6 INTs - 0-3, a winning percentage of 0.000

These are based on all playoff games in the Super Bowl era.  The data is courtesy of Cold Hard Football Facts.

As I have shown before, a QBs likelihood of throwing interceptions has been decreasing over time (based on the increasing value of that component in the QB Rating).  So, if one were to look at this season's regular season stats, I'm sure this table would look even more skewed.  (I don't have 2008 game by game data handy).  The point is still the same - throw INTs, and you dramatically reduce the likelihood that your team wins.  The fact that someone threw 5 picks is actually quite irrelevant.  Once you throw 2 picks, you're likelihood of winning is dramatically reduced, and it's less than 1 in 5 if you throw 3.

Ok fine, so let's look at both QBs in this game Jake Delhomme and Kurt Warner.   According to the table below, in Jake's career (including prior post season games), he had never thrown 5 INTs in a game.  However, he had thrown at least 2 INTs in a game 22% of the time, and at least 3 INTs in a game 6% of the time.  What's perhaps most interesting is that Kurt Warner had thrown at least 2 INTs in a game 28% of the time, and 3 INTs in a game 12% of the time.  

So, what does this all mean?  We need to look at the second table (see below the first table for the analysis).

According to this table, based on the likelihoods shown in the previous table there was an 18% chance that at least one of the QBs in this game was going to throw at least 3 INTs (see the last column in the table below).  That's a about 1 in 5.  That's much higher than I would have thought.  That's actually a higher likelihood than both QBs finishing the game having thrown 0 INTs.  Now admittedly, the likelihood that it was Delhomme and not Warner that was going to throw the 3 or more INTs was 2-to-1 against (given at least 1 QB would throw at least 3 INTs).  But the fact is, there was a pretty good chance that this was going to be a game where at least 1 QB threw multiple INTs.  Heck, there was about a 1 in 14 chance that at least 1 of them was going to throw 4 or more INTs - again, much higher likelihood than I would have thought (and you too, I'm guessing).

So there you have it.  An unexpected result.  Certainly.  But not that unexpected.  What should also be clear is that if you throw a pick, you're chances of winning reduce quite significantly.  And for each subsequent one, the odds of winning decrease exponentially.  After 3 picks, it's lights out.

NFL DIVISIONAL PLAYOFFS - Predicting the Winners

My intention with this blog was not to get into the prediction business, but I can't help myself. It is what I am trained to do. I like building models, and of course, "predicting" is a natural outcome. Although my focus with this blog is quarterbacks specifically, I thought I'd go out on a limb and expose a new game predicting model that I'm working on. Admittedly, my model doesn't have the sophistication of the models built by guys like Brian Burke over at AdvancedNFLStats.com, or Aaron Schatz and his team at the Football Outsiders (see their AFC predictions here, and their NFC predictions here). That all being said, I think I will continue to work on it over time, and, why not, let's put it to the test to see how mine stacks up.


The table below shows my predicted outcomes, assuming each team behaves 'as expected'. Of course, the football isn't round, and funny things happen when the ball bounces. The weather is another element that is not incorporated explicitly into the model.


Arizona at Carolina - All three of us agree that this is the 'easiest' game to predict - with Carolina winning handily. Vegas oddsmakers say a spread of 9.5/10 with the over/under at 48.5/49.0. My model concurs.


Baltimore at Tennessee - Should be a close game. FO calls it for Baltimore, and ANS calls it for Tennessee. My model suggests Tennessee in a close game. Vegas oddsmakers say a spread of 3.0, with the over/under at 34.0/35.0. I agree with the spread, but my model suggests more points (perhaps I need more work on my model)!


Philadelphia at NY Giants - Awfully close game - closest of all the games this weekend - FO on the one hand says Philly, but then he hedges and says its going to be really, really close (a pick 'em). ANS is a little more bullish on the Giants (he also hedges his bet and says, it's a 50-50 outcome if analyzed based on the whole season). My model agrees with both of these models/predictors, and says Philly in a squeaker. Vegas says G-men by 4, with the over/under at 40.0. My model says closer game than that, and a few more points (remember, Vegas needs to take 'perception' into account, as all they care about is getting half the money on one side and half on the other).


San Diego at Pittsburgh - FO says Pittsburgh, and so does ANS. I agree, with my model suggesting Pittsburgh buy more than a field goal. The oddsmakers in Vegas suggest a 5.5/6.0 point game, with the over/under at 37.5/38.0. I think it's a bit closer, but also a few more points.


This is the first public exposure of my model. I'll see how it does this weekend, and continue to build/improve it. Hopefully, at some point in the 2009 season, I'll be comfortable enough to share more details as to the inputs. Suffice it to say that I feel comfortable enough to expose it today.


Let's play the games!


We can evaluate how we did on Monday.