Comparing current NFL draft prospects to those of years past is standard procedure in draft evaluation, though most comparisons are built on the memory recall and subjective opinion of the particular evaluator.
This will be the first in a series of articles comparing the 2021 draft prospects to prior years and picking out the most similar comps with a clearly delineated and quantifiable method.
PFF data scientist Eric Eager has done tremendous work building college-to-pro projections, which are built off the robust college data we’ve collected since 2014 and have been applied to exercises like building an “Analytics” Mock. In this analysis, I will use some of our advanced stats for comparison but primarily rely on traditional stats to go back further to compare the 2021 prospects to draft classes going back to 2006.
Without the NFL Scouting Combine this season, the important measurables like weight and 40-yard dash will be reported through the various pro days that will be taking place over the next few weeks.
View PFF's 2021 NFL Draft position rankings:
The comps below were derived from a two-step process. First, I converted all the most statistically relevant stats and measurables to percentiles based on the thousands of prospects who have entered the NFL since 2006 at each position. Then, I filtered the total universe of past prospects by those who had draft positions, weight and 40 times within a 10th percentile in either direction of Khalil Herbert. For undrafted players, I assigned a numerical draft position of 300.
The rest of the matching features were transformed by principal component analysis (PCA). I found the closest statistically comparable players by the euclidean distance between the players' principle components, listed in the top 10 below.
The metrics for PCA are: rushing attempts per game, rushing yards per game, rushing touchdowns per game, receptions per game and market share of team receptions. All of these data points come from the prospect’s best collegiate season. I also matched the prospect’s market share of total team yards and touchdowns to past draft prospects.
For Herbert's draft position, I’m using an estimate based on the mock data collected at GrindingTheMocks.com. For the weight and 40 time, I’m using the numbers from his pro day, with a 0.03-second penalty added to the 40 time to reflect the uncertainty of pro-day timed measurements.
Most comparable players
Herbert had a good, not great, pro day, highlighted by his 4.46-second 40-yard dash at 211 pounds. The rest of Herbert’s drills were lackluster, but he displayed a ton of explosion on the field.
— ACC Football (@ACCFootball) December 13, 2020
Herbert recorded the second-most career 50-plus-yard carries (10) in the 2021 class.
The traditional stats don’t highlight Herbert’s big-play track record, but it is somewhat reflected in his strong market share and yards-per-game numbers, with relatively low usage for a lead back.