ahhh, but that is the point these days..the Aussies have kind of opened up a new 'style' of play in tests, where by scoring quickly is the way to win tests these days.
The opposition tends to feel that they need to follow suit (I dont think they do need to always)..if a team doesnt score at over 3 an over these days,it would appear that everyone thinks they are shooting themselves in the foot (they may be they may not be, i dont know). If a team scores only 60 in a session (even for the loss of no wickets) it is almost considered a waste of a session for the batting team, in that they have not really pushed the game in anyway, and by doing that may well have given the bowling team (Australia or whoever) the upper hand.
Now that sort of pressure does get to a player..and that is all players from time to time..probably the only one I can think of who doesnt seem to be affected by this is Dravid and even then I am sure the pressure of a slow moving scoreboard gets to him occassionally. it is human nature, and that is the way cricket is going these days...patience is now not really considered a virtue in test cricket anymore.
And that is where a bowler like mcGrath fits in....his strength is playing on the human weakness of impatience. He tucks a player up, he gets awkward bounce thanks to his height...he makes it hard for batsmen to score runs......i know ideally a batsman should just ride this out and not take chances...but everyone does..again that is human nature, to sieze the opportunity of personal gratification when it has been denied for so long.
So 20 balls of perfect 'corridor of uncertainty' bowling may not take the wicket, maybe ball 21 might be a wide one there to drive,and it may go crashing into the boundary after the batsman has reach out for the drive..but I would guarantee you that if that happens,a bowler like McGrath stores that away, so that in another 3 overs time, he might just let a 'loose' one go that bit wider..and i will tell you,those Aussie slips would be just waiting for the snick.
that is what pressure is all about a lot of the time...