Above is a brief vid of Andy doing drills on clay. I think drills are an important part of training, but I also think the body becomes programmed to do certain things, and it should be 'tricked' at times to help it deal with the unexpected. I'm a certified fitness instructor and used to train an amateur footie team (years ago).. but they asked me to help them because their trainer just did the same old stuff week in and week out.
With me, they never knew what was coming next. Oh the fun I (oops.. 'we') had...
.. and they did start to play better.
I'm really no expert at this... just an observation I had when I've watched Andy's other training vids on his official website... and for all I know, all the players do the same type of stuff.