December 24, 2012

Is Mark Sanchez as bad as Sports Chart of the Day says he is? Here’s some context.

After week 14 of the NFL season, Cork Gaines more or less blamed the poor performance of the NY Jets on Mark Sanchez, saying:

Last night, Mark Sanchez turned the ball over five times, continuing a disturbing trend over the past two seasons. He now has a league-leading 24 turnovers this season (17 int, 7 fumbles lost) and 50 over the last two seasons combined. In his first two seasons, Sanchez turned the ball over just 37 times.

Corked followed this up by publishing this chart on Business Insider’s Sports Chart of the Day.

QB Turnovers

I thought “Wow, Sanchez really is terrible!”  But I’m an Eagles fan, and we know terrible football.  This got me thinking about Michael Vick.  He was absolutely HORRIBLE turning the ball over the first few weeks of the season before he got a concussion and hasn’t played since.

In Cork’s chart, Vick is at #11, but he’s only played a full season in the NFL once.  So far in 2012, Vick has 19 turnovers in 9 games, for a turnover rate of 2.1 per game.  This puts Vick at #2 on the turnover rate ranking ahead of, you guessed it, Mark Sanchez.

What this should tell you, as it did to me, is that Cork’s chart isn’t normalized.  Sanchez has played more games that Vick at a slightly lower turnover rate, so of course he’s going to have more turnovers.

I decided to look into this farther and gathered data through week 15 from Pro-Football-Reference.com and built this viz.  (Download the data here.)  BTW, if you ever need pro football data, this is by far the easiest place on the internet to find what you’re looking for.

I started with turnovers, as Cork did, and if you sort by Turnovers on the right, you see that Sanchez is now third on the list, granted he was benched for week 15.

Change the sort to Turnovers per Game and Sanchez is now sixth.  Rex Grossman is first in turnover rate.  No wonder he hasn’t played this year.

It was important to me to also look at win percentage to see how turnovers might correlate to winning.  Change the sort to Win % and you can clearly see that those QBs at the top (the best winning percentages) have very low turnover rates, Andrew Luck being the exception, but he has seven game winning drives this year, which is a crazy number.

You can explore the relationship between turnovers and win % a bit deeper on the 2nd tab (Win % vs. Turnovers).

I chose to use a lollipop chart for these first three views.  I could have chosen a dot plot, but I wanted to emphasize both the end point and the length of the bar, but I didn’t want to clutter the chart too much with a bar chart.

I then wanted to see how who has improved or regressed from last year.  We do have one game less, so take that into consideration.  This view confirms that Sanchez is worse this year from a turnovers perspective: 28 in 2011 in 16 games and 29 in 2012 in 14 games.  Not good Mark!

For this view, I chose to use a bar chart for 2012 with 2011 as reference line.  But it’s not really a reference line.  It’s a dual axis chart with 2011 as a Gantt bar.  For me, this view works because it gives me a quick comparison between the last two seasons. 

I finish the viz off with a dot plot comparing fumbles and interceptions, each of which you can sort by on the right.  Ryan Fitzpatrick threw 39 interceptions last year…39!  That’s really hard to do.

I chose a dot plot for this view because I wanted an uncluttered view of two measures on the same chart, and I was only concerned about their relationship to each other, not their length.

There’s an immensely larger number of analyses you can perform on this data set.  I’d be curious to see if anyone can find any hidden relationships.  Give it a shot and post a comment if you find something useful.

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