Is Matt Cassel The New Tom Brady?

Matt Cassel of the New England Patriots is having a good year.  He is 13th in the NFL in Passer Rating, after 14 games.  And, in what may seem eerily similar to one Mr. Tom Brady, he replaced Brady in the first game of the season, when Brady was lost to the season as a result of a leg injury.  Flashback to  September 2001, and the aforementioned Brady, replaced Drew Bledsoe as the quarterback of the New England Patriots.  The rest, as they say, is history.

That year, Tom Brady had a great year.  A dream year.  Replacing Bledsoe in the 2nd game of the season, he went on to lead the Patriots to an 11-5 regular season record, and on to win Super Bowl XXXVI, 20-17 over the St. Louis Rams.  Brady was selected to the Pro Bowl, and was named Super Bowl MVP.  He finished 6th in the NFL in passing, with a Passer Rating of 86.5, and he had a CMI of 0.552 (see the table below).  That year, the league average CMI was 0.497, and his CMI was 1.25 Standard Deviations above the average.  Only Rich Gannon (2.54), Kurt Warner (1.57), and Jeff Garcia (1.33) had a better year that year.  

The graph below the table shows that he started out a little slow (understandably so), and played fairly consistently throughout the year, with a few spectacular (and one not so spectacular) games thrown in.  He didn't throw an interception in his first five games, but then threw 4 in a 31-20 loss at Denver in game 6.  All in all, he didn't throw a pick in nine games, the Patriots going 7-2 in those games.

So, how is Matt Cassel doing trying to imitate Tom Brady?

As mentioned earlier, his current Passer Rating is 87.1, a shade higher than Tom Brady's 86.5.  His CMI is 0.568, also better than Brady's 0.552.  He has six games to-date where he has not thrown an interception, leading the Pats to a 5-1 record in those games.  So how does Cassel's CMI of 0.568 compare to Brady's 0.552?  This is where the comparison ends.  In 2008, the league average CMI is 0.542, so Cassel's performance is 0.49 Standard Deviations above the average.  Good, but not great.  Good for 9th out of 30 quarterbacks who have thrown enough passes to qualify.  The table below shows a game-by-game comparison of Cassel's performances compared to Brady's 2001 season.

A Slight (but necessary) Digression

Brian Burke, who does some excellent analytical work at advancednflstats.com has made this observation regarding three first-year quarterbacks - Joe Flacco of Baltimore, Matt Ryan of Atlanta, and Matt Cassel of New England.  He suggests that their performance has been improving as the 2008 season has moved on. and shows their performance, graphically illustrating it in the following manner.  He uses a measure, "Adjusted YPA" or, Adjusted Yards per Attempt, defined as [Yards -40*Interceptions + 10*Touchdowns]/Attempt, and then looks at their 4-week moving average to compare the three quarterbacks.

Well, I decided to look myself.  I have been "casually observing" that Flacco and Ryan have been having some "pretty decent" games recently (Ryan is on my Fantasy team).  So, I decided to put my newly developed CMI to the test.

Here's what it shows:

It appears to be very consistent with what Brian found.  Matt Ryan has improved the most.  CMI shows that Matt Cassel has in fact had the least improvement, if any.  However, to his credit, he has been performing at a very high level from the beginning.  Looking at the table below, you see that both Ryan and Flacco have remarkably similar attempts and completions through the first 12 weeks, with their only difference being the # of interceptions thrown.  Also, you can see that Cassel attempts more than 5 passes per game more than the other two (partially reflecting the fact that New England has no running game).

Brian has, in the past, ventured into the "creating a new passer rating" space, and, in fact, created one.  He uses a concept called "Air Yards", defined as, [Yards - Yards After Catch] to relate "passer rating" to a team's wins and losses.  See his post here.  I agree with his approach generally.  In other words, if you look at his formula, it's a lot like CMI.

QB Wins Added = [(Air Yards - Sack Yards) * 1.56 - INTs * 50.5]/Pass Attempts - 3

where, (Air Yards - Sack Yards) is substituted for Completions.  In other words, he also takes out Touchdowns thrown and Yards per Attempt.  Brian is the first person I know of that does not include touchdowns as a part of a passer rating calculation, and he is to be commended for that.  My only real issue with Brian's calculation is that YAC, or, Yards After Catch, is not a readily available statistic, and hence, "Air Yards" is not easily calculated.

I am still developing CMI, and the next (enhanced) version will incorporate sacks.  Given that one of my goals is also to look back in time and be able to compare QBs over time, I will only be able to that back to 1969.

As I mentioned at the top, Brian is a very smart guy, and has done some very good work on a whole host of topics relating to the NFL, with particular attention to statistical rigor.  I will be referring to his site quite a bit in future postings.