Groucho
Greg Davis (50)
Speed training does improve your Power. Obviously not as much as specific Power training, but still.
Perhaps by "powerful" he means in terms of play rather then literal Muscular Power.
Acceleration training increases explosive strength. By contrast, energy for speed is supplied by the anaerobic alactic pathway. This speed component of anaerobic metabolism lasts for approximately eight seconds and should be trained when no muscle fatigue is present, such as by running 30 and 60 metres while running at 95% to 100% of maximum. It is quite hard to design exercises that benefit both strength and speed, other than co-incidentally.