Of all the players I've coached and played with in club rugby, for England and for the Lions, and of all the players I've coached and played against, there remain only two backs I consider to be the complete article - Jonny Wilkinson and Brian O'Driscoll.
At their peak, these two players have everything in attack and defence. They are outstanding in the way they influence the players around them and are a credit to the game in the way they operate off the pitch.
The first time O'Driscoll looked special was against France in Paris in 2000, when he scored a hat-trick.
The significance was that we were seeing a centre with electrifying speed. Back then, he was a slimmed-down version of the more muscular player he is today. He was incredibly quick and elusive.
For myself and England defence coach Phil Larder, it was his attacking threat that was our big concern.
In the Grand Slam game in 2003, we worked on a plan to man-mark him with three players, so the tackler was not exposed by O'Driscoll's footwork and pace in a one-on-one situation.
That's how big a threat we believed he was - he needed three men to handle him. Ireland were going for a Grand Slam, but none of the players around Brian were in the same league.
Whenever he had the ball we wanted one player opposite him and one man either side - it would usually be Wilkinson, Will Greenwood and Mike Tindall.
The trick was to get on to him quickly and shut him down, give him no time or space in which to run. For the first quarter of that game the scores remained close, but Ireland had the bulk of the ball.
Wilkinson got on top of O'Driscoll more than any other player, making 20 tackles in the first 25 minutes.
Shutting down O'Driscoll shut down Ireland. While he may no longer have the lightning pace of his youth, Brian has worked hard on his skills at Leinster with head coach Joe Schmidt.
His handling is now a great asset to the Irish attack, as we saw with that sublime pass to Simon Zebo to set up the opening try against Wales.
He was my No 1 choice to captain the Lions in 2005. I had four rules to picking my captain: he had to be in the Test team, he had to have earned the respect of both his own side and the opposition, he had to be an experienced captain with undoubted leadership skills and he had to be someone I knew I was going to get on with.
I telephoned him in Dublin and invited him over to our house. I wanted to get to know Brian and speak to him in person. We kept it quiet. He flew into Heathrow and I picked him up at the airport.
We sat down for dinner and I was immediately impressed, so I wasted no time in telling him I wanted him to be Lions captain.
As everyone surely remembers, Brian was injured in the first 90 seconds of the first Test against the All Blacks as a result of Tana Umaga's tackle. In the build-up to that Test, even in training I just could not believe Brian's strength in defence.
We'd always focused on him in an attacking light, but he's a role model in the tackling area with his trademark of getting over the ball.
Once he's made a tackle, a supporting player has to get there really quick and hit him incredibly hard to clear him out because once he gets into that flanker's position over the ball he's unbelievably difficult to move. O'Driscoll is right to try to steer clear of discussing retirement.
I made a big point in the build-up to the 2003 World Cup of telling my squad that any player who talked about retirement would not come to Australia. The World Cup, the Lions tour, the Six Nations, these tournaments are not retirement parties.
The French made a huge mistake in 2003 when Fabien Galthie, their captain, announced he would be retiring after the World Cup. Once the news was out, it became all about him. You should retire when you are ready to retire, without making any declarations of intent or premature announcements.
To play like Brian did against Wales last Saturday after losing the captaincy to Jamie Heaslip - throwing everything at those big centres and leading the defensive line - tells you everything about his character. He does his talking on the pitch.