The great Stanley Matthews was noted for his devastating acceleration A member of the press once asked him how fast he could run 100 yards, and Stanley said he had no idea - ("when does a footballer run 100 yards?") Matthews trained for 15 yards down the side of the box, and particularly for the first four yards from a standing start. He reckoned if he could be four yards away by the time the defender turned, then that defender had not only to be as fast as he was, but 20% faster to catch him before he got his cross in. And it was mathematically perfect! So tell me when a footballer uses a tennis ball please. Those old guys really did know their stuff, y'know
I can still probably do 100 with a football (if I'm given about an hour and 30 failed attempts to do it) but I'd be proud of 5 or more with a tennis ball. Must be solid.