After doing my initial blog looking at how much each team is spending per position group. I wanted to take a look to see if there was any correlation between how much teams are spending on a position group and winning. To do this I needed to merge the cap data from spotrac and season summary data from pro-football-reference . I merged these datasets over the last 5 years but it’d be interesting to try and find data since the salary cap was in place(1994). Here’s a graph of my yearly findings for the last 5 years(2011-2015).
Quick review on correlation from Pearson:
- .00-.19 “very weak”
- .20-.39 “weak”
- .40-.59 “moderate”
- .60-.79 “strong”
- .80-1.0 “very strong”
As you can see from the graph the correlation numbers aren’t exactly high. I believe that’s because the best players aren’t necessarily getting paid the most money. For example, before last year Russel Wilson was on his rookie contract and the Seahawks were making the playoffs year after year and only paying Russel $749,176 a year. Now he know doubt had a lot to do with the Seahawks winning before and going forward but his Salary before his new contract wouldn’t have correlated much to winning. Examples like this can be found at each position. This is why it’s necessary to have a good Front Office to continually bring in young talent that can contribute at a lower price. Looking at actual on the field stats and trying to correlate would be a much better exercise than trying to merge cap data with correlation.
Over the last 5 years there’s not one correlation that’s greater than ‘very weak’. But the positions that do have positive correlations DB, LB, QB, and WR are the positions that GM’s over the last 5 years have been willing to pay. Left Tackle is another position that has been getting paid very well in the league because Left Tackle’s are usually the one’s protecting a QB’s blind spot.
This data emphasizes the importance of drafting well because spending money on a particular position does not correlate with your team winning. Also interesting to note the positions that do have positive correlations must be that way because those players have made it to their second/third contracts and are now getting the big contracts. So it makes me wonder if DB, LB, QB and WR are the positions that have the longest careers in the NFL.