The 40-yard dash is one of the most popular drills at the combine as tenths of a second can greatly affect a player's future. Players are timed in 10, 20, and 40 yard increments to see how quickly they explode off the line and how quickly they reach the top speed.
"This is where all the players make their money at," Pittsburgh Steelers college scout Mark Gorcsak said. "The fastest you are, the most likely the higher your stock is going to be and the higher you get drafted."
The 10- and 20-yard times are also key components to scouting a player's speed, particularly those in the skill positions.
"We time the 10 to see how fast a player can get off, and if you're a DB, wide receiver or a defensive player that's the closing speed," Gorscak said. "With the 20, we're looking to see if you have any long speed ... if you build the speed, or if you remain at one speed."
While the 40-yard dash is a fan favorite, NFL scouts also consider the 10- and 20-yard dashes, as well as 20- and 60-yard shuttle runs and cone drills, as measures of a player's agility and speed.