Before you look at all the data below, remember that the sample is looking at NFL seasons two through four. This isn’t analyzing entire NFL careers. This is just designed to find the best running backs for their rookie contracts. It’s up to you if you want to extrapolate the data to either rookie seasons or seasons after the rookie contract. I’m guessing the data would be pretty similar, but the exact correlations would be slightly different.
Before we look at the correlations, I wanted to note that Approximate Value is nowhere near the best measure for ranking cornerbacks. However, it’s not completely worthless. Here are the top-5 corners in the sample: Richard Sherman, Darrelle Revis, Patrick Peterson, Jalen Ramsey, and Courtland Finnegan.
The NFL Combine has historically been more important for corners than on-field counting stats production. If you’re spending any time looking at any of the tackle stats, your process is flawed. If you’re looking at interceptions or pass deflections, then your process is flawed, but it’s less flawed then looking at the tackles stats. Instead, we need to be heavily using Sports Info Solutions and Pro Football Focus coverage stats. I don’t even need historical data to know that those metrics would outperform any of these counting stats.
Of the NFL Combine measures, the speed score has been the most correlated to early NFL success historically. However, it still isn’t very strong. My understanding of the position is that it’s so based around instincts -- both reading the receiver and, at times, the quarterback -- and it’s harder to quantify that at the NFL Combine or through counting stats. If forced to use a minimum to find elite corners, I’d set it at 90 since all 10 corners with at least a 0.50 AV/G were above that mark. Unfortunately, that will only eliminate a handful of corners each season.
Safeties (Under 210 pounds)
I didn’t have the free or strong titles in my database, so I opted to separate the two positions by weight. Of course, this is a flawed step, but it’s an improvement over just lumping all safeties into one so deal with it. … For the smaller safeties, a lot of things are somewhat important but no single statistic was very strong. When it comes to the on-field counting stats, total tackles and pass deflections are arguably the two best, but once again, it’s a weak correlation.
While the trend isn’t strong, we can use a minimum threshold to find out what the elite safeties look like. 14 of the 18 safeties (78%) who had at least a 0.40 AV/G in NFL seasons two through four ran under 4.52 second during the 40-yard dash.
Safeties (Over 210 pounds)
The heavier safeties have slightly different correlation coefficients than the safeties who weighed under 210 pounds. College solo, assisted, and total tackles had a negative relationship with early NFL success for the smaller safeties, but it’s a zero or weakly positive relationship for the big boys. On the flip side, the college interceptions and pass deflection stats have a negative relationship with early NFL success when it was slightly positive for the smaller safeties. These explain the differences in roles between heavy (strong) and skinny (free) safeties.