Albert Pujols, right on time!
Never be late on a fastball in a fastball count!
The saying I grew up hearing was "be ready for the fastball and adjust to anything off-speed." The point was, if you are prepared for the fastball then you'll still have the ability to keep your hands back a little longer to hit an off-speed pitch. Gear up for an off-speed pitch and even an average fastball will be blown right past you.
It's understandable that hitters may be a bit late on a fastball when the pitcher is way ahead in the count. In this case, the hitter must be prepared for anything that may be thrown and cannot simply prepare for only a fastball. However, in fastball counts like 0-0, 1-0, 2-0, 3-0, and 3-1, there is absolutely no excuse for being late on the fastball that will probably arrive next.
Hitting is hard. However, hitting is less hard in fastball counts because you practically know what's coming. So, if you are a player, be on-time in fastball counts and your average (and power numbers!) will most likely go up.
It may also take some stress off your coach!