Speed most definitely can be coached. There are two major parts that must be coached. The first is mechanics. The system best utilized is the PAL system: Posture, Arm action, Leg action. A variety of drills can be used to coach mechanics. If you improve mechanics, you will improve speed. The second component is training the neuromuscular system with reactive drills using visual or auditory cues, and also integrating competitive linear speed and lateral agility drills with two or more athletes. Seed can be improved by strengthening the legs. If you can apply more force to the ground you will run faster. You can then use specific coaching points keeping force application in mind. For instance in the pro agility athletes can be instructed to cover the first 5 yards in 3 steps, the next 10 yards in 5 steps, and the last 5 yards in 3 steps. In the 10 yard sprint or start in the 40, athletes can be instructed to try and cover the first 5 yards in 3 steps. The bottom line is you improve acceleration by strengthening the legs, developing ground-based power, and working at the proper work to rest ratios; you improve agility by strengthening the legs, developing eccentric strength, and running sport-specific drills at the proper work-to-rest ratios.