I agree with the time clock. I think it would be helpful. If I were a player, after every point I wouldn't be thinking, "OK, I have just 25 seconds to get my thoughts together and serve." I would be thinking, "OK, what do I need to do to win this next point." I wouldn't even be thinking about time and how long I was taking. These guys are trained athletes and are trained at closing their minds to any distraction besides the match at hand.
Personally, I just assume playing by the rules is 'the match at hand'.
From my perspective it is flat out gamesmanship, an attempt to control the tempo of play. If you watch carefully you will see that it begins in the locker room!!! Rafa makes every opponent wait for him at every opportunity.
1. Coming out of the locker room.
2. At the coin toss.
3. Both serving and returning.
4. During change overs.
The only real problem is #3 because it is a time violation. Both Sharapova and Djokovic are guilty of this as well. Most umps and players are either are afraid to make the call him or just don't care.
I think this is a direct contradiction with Rafa's otherwise humble and genuine character.
As I've said before, if these players could clean up this aspect of their game it would be another feather in their cap.
Bring in the time clock!!!