April 04, 2015 - Tony Villiotti
Comparing Draft Years
Every year experts offer up their opinions on the upcoming draft, both on the overall depth of the class and the quality and depth by playing position. In this article we will explore how real these differences are and the degree of difference among draft years.
Year-to-Year Comparison
What is the best way to measure the differences? There is no perfect metric, but the most practical performance metric is the number of games started. Number of starts has the principal advantage of letting us use recent years in the analysis whereas other measures (such as number of five-year starters) required us to cut off the analysis well before the most recent drafts.
There is an inherent conflict between using current information versus complete information. It takes 15 years or so to “complete the book” on a draft class. This would mean that the most recent year that could be used in this analysis is 1999. That serves as a sound basis for the analysis but many readers would regard the information as stale and, therefore, not relevant.
It was decided to compare draft classes after their first, third, fifth and seventh years. The draft years used were the most recent 10 drafts for which the number of starts data was available as follows:
The following table summarizes the data by draft class for each of the four time periods. The “ratio” row represents the ratio of the number of starts for best draft compared to the worst draft. A high number shows a lot of variation and a low number shows little variability.
This table shows that the degree of difference, as expressed by the ratio, is greatest for the first year and levels off after that. The 2006 draft year has held up best over time. The draft class in each of the last four years has exceeded the number of first-year starts from 2006 but both 2011 and 2012 have fallen behind 2006 by the end of the third year and it is too soon to tell for 2013 and 2014. It remains to be seen if the advantage of the 2006 draft class will hold up.
The 2008 draft class is also an interesting case. That class is ranked last in first year starts but moves up to the middle of the pack for the subsequent measurement periods. This reinforces the notion that the first year does not tell anywhere near the whole story when it comes to evaluating draft classes.
This analysis shows that there is a reasonably large difference among draft years. This makes characterizing draft classes as good and bad a logical exercise.
As an aside, data from the draft classes that are virtually complete as far as number of starters (1995-1999) is instructive regarding the evolution of the impact of a draft class. The cumulative average percentage of total starts by year for the five draft classes is shown in the following table. The table tells us that 91% of the starts from a draft class occur in the first 10 years.
Playing Position Comparison
It should be no surprise that the level of variability increases by playing position. There are fewer data points and this leads to greater variances in results. The analysis by playing position was confined to the most recent ten draft classes and excluded fullbacks and special teams players. Again, the number of starts was used as the performance metric.
The following table shows the best and worst classes for each playing position after one season by draft class.
This table shows that there significant differences among playing positions with the offensive line and defensive backs showing the smallest, though still significant, differences.
The next table shows the same information after three years for each playing position by draft class (which excludes the 2013 and 2014 draft classes).
This table shows that the ratios have tightened significantly by the third year but that they still exist. Offensive linemen show the smallest difference between the best and worst year with running backs having the largest difference.
It is interesting to note that while 2006 is a highly rated draft class, it does not appear as the best year for any playing position.
Follow Tony on Twitter @draftmetrics
The following table summarizes the data by draft class for each of the four time periods. The “ratio” row represents the ratio of the number of starts for best draft compared to the worst draft. A high number shows a lot of variation and a low number shows little variability.
This table shows that the degree of difference, as expressed by the ratio, is greatest for the first year and levels off after that. The 2006 draft year has held up best over time. The draft class in each of the last four years has exceeded the number of first-year starts from 2006 but both 2011 and 2012 have fallen behind 2006 by the end of the third year and it is too soon to tell for 2013 and 2014. It remains to be seen if the advantage of the 2006 draft class will hold up.
The 2008 draft class is also an interesting case. That class is ranked last in first year starts but moves up to the middle of the pack for the subsequent measurement periods. This reinforces the notion that the first year does not tell anywhere near the whole story when it comes to evaluating draft classes.
This analysis shows that there is a reasonably large difference among draft years. This makes characterizing draft classes as good and bad a logical exercise.
As an aside, data from the draft classes that are virtually complete as far as number of starters (1995-1999) is instructive regarding the evolution of the impact of a draft class. The cumulative average percentage of total starts by year for the five draft classes is shown in the following table. The table tells us that 91% of the starts from a draft class occur in the first 10 years.
Playing Position Comparison
It should be no surprise that the level of variability increases by playing position. There are fewer data points and this leads to greater variances in results. The analysis by playing position was confined to the most recent ten draft classes and excluded fullbacks and special teams players. Again, the number of starts was used as the performance metric.
The following table shows the best and worst classes for each playing position after one season by draft class.
This table shows that there significant differences among playing positions with the offensive line and defensive backs showing the smallest, though still significant, differences.
The next table shows the same information after three years for each playing position by draft class (which excludes the 2013 and 2014 draft classes).
This table shows that the ratios have tightened significantly by the third year but that they still exist. Offensive linemen show the smallest difference between the best and worst year with running backs having the largest difference.
It is interesting to note that while 2006 is a highly rated draft class, it does not appear as the best year for any playing position.
Follow Tony on Twitter @draftmetrics
