David Flatman: My man of the tournament is peerless Weepu

Every rugby coach has, in order to relieve his charges of some psychological weight, described an upcoming encounter as "just another game". Of course every match is, by definition, just another one, but we all know that one always arrives which holds more significance than is usual. At every level – from pub to professional – there are some games that rank as vital where others actually fall into the slot marked "important".

It is easy to quip that any game at a Rugby World Cup should be regarded as vital, but this is stretching the truth for the purposes of romance.

When England took on Romania they did so with comparatively littlepressure and with, I suspect, much reduced anxiety. As you might expect,lots of players find it easier to perform well in these circumstances.

There will be some, however, who feel they need the massive pressure of a whopping match to get the best out of themselves.

The thing is, if you want to be a truly world-class player, you have to be close to immaculate as often as possible, not just in the easy matchesand not just in the big ones.

With this in mind – and having watched every match of this Rugby World Cup – I think the best player has been the All Black scrum-half Piri Weepu. This might cause a stir should you be a relative of Sean O'Brien or David Pocock, but that's OK; it's only an opinion.

I have watched him play against varying grades of opposition and the one thing I have noticed above all else is that his game has never altered one jot; it has never dipped.

Now consistency isn't everything, I know, but the mean standard of his rugby has been something approaching flawless. His core skills – passing, communicating, box kicking and keeping his opponents honest closest to the breakdown – have been so strong that he has now become the heartbeat of his team. He embodies the Kiwi ethos of doing basic things so well that, whether your opponents know it's coming or not, they can do nothing about it.

Watch the whole team and you'll notice that these basics are the foundation of their game and always – without exception – come before the flashy, flamboyant stuff. Their simple plan and attention to detail is what sets them apart, and Weepu is the arbiter in chief.

We all agree that a good deal of this sport is about mental aptitude and that the need to be big and strong – though important – isn't all it takes. Weepu – and I don't say this in criticism – doesn't look like many other scrum halves. When you think of just how much running, jinking and bending down a scrum-half does in a game at this level, it is not surprising that most of them look lean as whippets.

Clearly, Weepu is incredibly fit; in fact, I haven't yet seen him look tired in this tournament. Perhaps the little bit of extra timber he carries around helps me relate to him, or perhaps he is just one of those guys who is so good that his body shape becomes irrelevant. Seriously, look around; from the quarter-finals onward, there aren't many of those.

So the two real tests for a player in a World Cup are whether he can, when required, rise above the mire in the group stages, and continue to inspire when the sharp end comes to pass.

To be honest, there were a handful of players in my mind who had done amazing things over the past few weeks. But I chose someone who, despite the prominence of his position, chose not to exercise his ego by turning peacock but to do what was right for the team, time and time again.

He has always been a brilliant scrum-half but during this World Cup he has, through his actions, become much more; he has become the most important player in the best team in the world.