Don't Always Trust The 40
The 40-yard dash is by most considered the mecca of the NFL combine drills. Tenths of a second in this drill can make or break a player's draft status. The irony in this however, is that the 40-yard dash tests a player's speed in a position that is extraneous to the positions that they would be in during a game. Nevertheless, this drill holds its significant amount of prominence in the combine and players are very aware. Athletes spend a great deal of time training to run the 40-yard dash, which includes adapting sprinting mechanics used in track in field to drop every possible fraction of a second from their time. However, many of these very mechanics that players adapt do not translate to the football field, and therefore the 40-yard dash is not necessarily a test of a player's football speed. One of the main strategies that players use when running the 40 is to keep their feet directly under their hips to eliminate any side stepping as seen here:
While this is an extremely effective sprinting method to ensure all of the distance covered by the runner with each step becomes forward displacement and none is wasted going to the side, it does not translate to the football field. Unlike in track, side stepping is essential in football because it gives a player the ability to cut and change direction at any given moment. When the feet are directly under the hips, all the force of the athlete's weight is straight down. On the other hand, when the feet are further apart, it introduces a horizontal component to the force which decreases the vertical force that the athlete has to fight against when decelerating into a cut. Therefore, it takes less time for a player to decelerate and allows them to change direction faster. Keeping a wide stance also allows a player to maintain a low center of gravity, which allows them to better control their movement when changing direction because it reduces the amount of torque on the body. This type of running improves body control, which then results in faster cuts, crisper routes, faster recovery in pass coverage, etc. Here, you can see how Frank Gore's side-stepping allowed him to make a sudden cut and change direction quickly without losing control of his body.
However, the 40-yard dash does not test for this kind of football speed, it instead tests for the track speed that does not translate to the football field. For this reason 40 times are at times a misrepresentation of a player's game speed. In last year's draft, Oregon running back De'Anthony Thomas speed was immensely misrepresented by his official 4.50 40 time. Being that he is a player whose chief asset is speed, a 4.50 in the 40 tremendously lowered his draft status. Originally projected as a first or second round pick, Thomas fell to Kansas City in the FOURTH ROUND and was undoubtedly the biggest steal of the 2014 NFL Draft. This is a prime example of how speed should not be judged by 40-yard dash times, and rather by the film, specifically plays like this:
During his college career, Thomas made innumerable plays like this, plays that should not be made by a 4.50 40-yard dash runner. Many of the defensive backs that could not catch him on this return are the same players who run 4.3-4.4 40-yard dash times. So, while fast players will obviously tend to run fast 40 yard dashes, a separation needs to be made between track speed and football speed, because they are clearly not the same thing.