Think of the open-side flanker as your 'rat-up-a-drainpipe' type player, if you will, or the 'groveller'.
Because defensive lines are so tight in the modern game, the open-side's role is turning rucks and mauls into continuity play again.
It's such an important role now, and that's one of area of the game that has changed so much since my playing days.
In the old days the benchmark was set by someone like Michael Jones. Back then he was seen as the new breed, the guy who forged the gap between the forwards and backs.
Jones created the continuity, he always seemed to be on the shoulder of the inside or outside centre or he was steaming up on the inside of the wingers to score tries.
There is a real art to modern open-side play and McCaw has mastered it
But the guy who first mastered the new wave of open-side flankers was former All Black Josh Kronfeld. England's Neil Back was another pioneer too.
The way guys tackle these days, they're not always looking to just smash the opponent back.
At the tackle area or a ruck situation, you're talking about a 50-50 ball, and often a tackler will be willing to sacrifice a few metres to get into a good position.
Their job is to then get the ball-carrier into a body wrap, pull him to the ground, get up in one movement and rip the ball.
Often the tackler will deliberately wrap up his opponent, knowing that eight times out of 10 the ball-carrier will be penalised for holding onto the ball.
Australia's George Smith and Phil Waugh are other stand-out guys but All Black captain Richie McCaw has taken the game to a new dimension.
I wouldn't say he's exactly a step-up from Kronfeld, but he's such a leader and has such a presence on the field which can change the direction of a game.
So there's a real art to modern open-side play and McCaw has mastered it.