Using 40-Yard Dash to Predict Cornerback Performance in NFL
The 40-yard dash can often make or break a player’s draft stock, but is the relationship between timed long speed and perceived value warranted? Although I think 40-yard dash times are largely overrated, I’ve often commented on the importance of the measurable for cornerbacks. Cornerbacks need to allow receivers to reach their hip, “sitting” on underneath routes and utilizing superior speed to catch up should the receiver run vertically. For this reason, I believe long speed is more important for cornerbacks than any other position in football.
I spent yesterday charting cornerback 40-yard dash times from 2001-2010. Only cornerbacks who ran at the Combine were considered, as I wanted to obtain as close to standardization as possible. I excluded rookies from this past season to eliminate some of the variance in career value which could result from a small sample size of games.
But how do we go about measuring individual value? There are a number of ways to determine a player’s worth, none of which are without their weaknesses. I chose Pro Football Reference’s weighted career approximate value. You can head there for the details of the AV formula, but games played, games started, sacks, interceptions, touchdowns and All Pro honors are all part of the equation. To balance peak production versus raw totals, weighted AV counts 100% of a player’s top season, 95% of his second-best season, and so on.
Below, you can see a comparison between weighted career AV and Combine 40-yard dash times. All times courtesy of NFLCombineResults.com.
As expected, there is a pretty strong correlation between 40-yard dash time and AV-per-season. The most noteworthy points of the graph come at the areas marked with stars, where there appears to be a fairly significant drop in NFL production. These declines come at the 4.40 and 4.55 marks.
Thus, it appears there are baseline speeds at which NFL players will experience much greater success if surpassed. The numbers seem to coincide with common sense, too. Sub-4.40 players possess elite speed which has exponential value. In all practical terms, the .05-second gap between a 4.34 and 4.39 is not nearly as important as that between 4.39 and 4.44. There are a multitude of players who run mid-4.4s, but few in the mid-4.3s. If a cornerback’s 4.35 speed is enough to shut down a receiver, does a jump to 4.30 speed matter? Of course more speed is always a good thing, but long speed variances in certain ranges appear to be more valuable than others, at least at the cornerback position.
The drop at the 4.56+ range may not look dramatic, but the decrease in AV percentage is pretty substantial. As a reference point, career AV drops about the same percentage at that point as at sub-4.40 to 4.40-4.41. Here are a few other interesting notes:
- The weighted career AV-per-season for players who ran 4.36 to 4.39 is 2.40, compared to 2.04 for sub-4.35 cornerbacks. Thus, 4.39 speed seems to be elite and a jump to the low 4.3s may not be extremely valuable.
- The weighted career AV-per-season for cornerbacks in the 4.4 to 4.5 range is 1.37, just a bit less than the 1.50 for cornerbacks in the 4.40 to 4.45 range. The drop from 4.49 to the low 4.4s is likely comparable to that from 4.39 to the low 4.3s.
- Of the 52 cornerbacks who have run a sub-4.4 from 2001 to 2010, 20 (38.5%) have a career weighted AV-per-season of 2.5 or more. The mean is 2.24.
- Of the 72 cornerbacks who have run 4.55 or greater from 2001 to 2010, just five (6.9%) have a career weighted AV-per-season of 2.5 or more. The mean is 0.58. Notable exceptions include Anthony Henry, Renaldo Hill and Terrence McGee.
Of course, using AV as a barometer for NFL success is by no means a flawless practice. The largest weakness with the method is that higher picks, who naturally see more playing time earlier in their careers, tend to be faster. The average draft round for cornerbacks who ran under 4.40 is 3.12. That number jumps to 4.94 for those who ran above 4.55.
To compensate for this, I plotted the AV of cornerbacks based on the round in which they were drafted. Note that I charted cornerbacks by how they ranked in their draft class in terms of their 40-yard dash as opposed to their actual time. This is to compensate for overall speed improvement over the last decade. In 2001, for example, the fastest time was 4.44 and only four cornerbacks checked in below 4.50. In 2010, four corners registered times under 4.44 (the fastest being 4.32) and 15 were under 4.50.
You can see above that, for the first two rounds, faster is better. The correlation between speed and AV is strongest here, with 12 first-round cornerbacks with a career AV-per-season of 2+ running a sub-4.40, and only two running 4.50 or greater. One of those two cornerbacks is Malcolm Jenkins, whose success in the NFL has come at safety. The other is Joe Haden, whose sample size of games isn’t staggering.
Also note that this first-round relationship between speed and success is not due to the highest picks in the round being fastest. Of the seven cornerbacks selected in the top 10 from 2001 to 2010, the average 40-yard dash time is 4.43. That number actually drops to 4.41 for cornerbacks selected between 11th and 32nd overall.
The same positive correlation between speed and NFL success runs into the second round. Of the second-round cornerbacks who have registered a career AV-per-season of 2+, seven ran under 4.40 and only three above 4.50, despite there being 11 total second-round cornerbacks under 4.40 and nine above 4.50.
Interestingly, the relationship we see between first and second-round cornerbacks’ timed Combine speed and their career value seems to flip once we reach the third and fourth rounds. There, slower cornerbacks have historically outperformed faster ones. As you can see below, this relationship extends to every round thereafter.
Since 2001, only two cornerbacks selected in rounds 3-7 have run a sub-4.40 and registered a career AV-per-season above 2.0. Compare that to 12 who have run 4.50+ and found the same amount of success. Considering the rate at which each category of cornerbacks is drafted in that range, we’d expect the number of “successful” mid-to-late round cornerbacks with elite speed to be about triple the current number.
But how could slower cornerbacks play better than faster ones? My guess is that, in the middle and late rounds when teams are seeking to maximize upside, they gamble on fast cornerbacks, knowing the correlation between speed and success at the position is a strong one.
The targeting of cornerbacks with elite speed might come at the expense of those with moderate speed who are simply superior football players. Players like Ellis Hobbs (third round, 4.45) and Asante Samuel (fourth round, 4.49) drop in favor of faster cornerbacks in the mold of Stanley Wilson (4.36), Marcus McCauley (4.39), Joseph Jefferson (4.39), Karl Paymah (4.35), Jonathan Wade (4.35), Scott Starks (4.35). . .and the list goes on.
Of course, no NFL team is going to (or should) bypass a faster player for a slower one based on that fact alone. But perhaps an emphasis on moderately-fast cornerbacks who can play football and aren’t simply track stars might be a good start. Here are a few other general rules for cornerback drafting:
1. In the early rounds when all prospects are pretty much immediate starters, emphasize speed.
There is no doubt that NFL cornerbacks with elite speed (sub-4.40) outperform those with moderate speed, and it is rare that a “slow” cornerback finds a lot of success in the big leagues. The career AV-per-season for cornerbacks who run 4.55+ is 0.59. Players like Joe Haden are few and far between, but Jonathan Joseph, Dominique Rodgers-Cromartie and Chris Houston-esque players are prevalent. At a time when you can have a great football player and one with elite speed, don’t bypass either trait.
2. In the later rounds, find football players with high upside, not athletes who run fast and happen to play football.
There’s no doubt faster is better for cornerbacks, but don’t overlook a potentially great football player who runs a 4.45 for a sprinter who clocks in at 4.35.
3. Know the “tipping points.”
4.32 is outstanding, but it isn’t significantly more valuable than 4.38. 4.38, on the other hand, has a lot more potential value than 4.44.
4. Don’t draft cornerbacks who run over 4.55.
There are always exceptions, but very few players can overcome being “slow” at cornerback. Blazing speed is valuable and good speed is adequate, but being in the bottom 30% of your draft class in 40 times is basically a death sentence for corners.
5. Undrafted cornerbacks almost never pan out (even more so than other positions).
While you can find undrafted gems in the NFL, doing so at the cornerback position is almost impossible. Of the 70 undrafted cornerbacks who went to the Combine from 2001 to 2010, 57 registered a career AV-per-season of zero. Only one (Jabari Greer) checked in above 1.25.
As a comparison, there have been 25 cornerbacks drafted since 2001 who have tallied a career AV-per-season of 4+. 11 of those have run sub-4.40 40-yard dashes, and only four have checked in above 4.50. Two of those four (Antrel Rolle and Malcolm Jenkins) moved to safety to do it.