The Lions realised they were maybe 18 months behind, if not longer, in their skill development, conditioning and overall vision on how the game could be played.
In the inevitable lengthy debrief, the conclusions were the Lions took too many players; too many older players and lacked, individually and collectively, the micro skills of the All Blacks.
Essentially, the Lions were playing a style of game that was bash and bash when it needed to be more bash and dash.
Here we are 12 years on and the picture is supposedly entirely different. The Lions of 2017 are using the blueprint of 2005 as their guide on how not to do things.
They are adamant they won't make the same mistakes and there is certainly enough noise being made since they picked their tour party to insist they haven't.
Yet there are themes running through the 2017 squad that are eerily reminiscent of 2005 and for all the predictions that this series will go to the wire, it could just as easily be as one-sided as it was last time.
The Lions are taking 41 players instead of the 37 they said. A late change of mind saw them add another four, raising the spectre, that just as happened 12 years ago, there will be a handful of tourists who gather dust - become a little twitchy and disruptive as a result of barely being involved.
Then there is the whole business of skill and style. And it's here where the Lions might find they have again showed up on the wrong planet.
They might find they have read too much into Ireland's Chicago victory over the All Blacks and seen things that aren't actually there.
The All Blacks, using their fourth choice lock and a flanker in their second row, were a horror show in the lineout.
They were just as bad for 50 minutes in other areas, but this doesn't confirm them as being unduly vulnerable against teams that target them in the physical and structured aspects of the game.
It merely says they played badly in the USA and that they are no different to any other test team - that if they don't front physically, they can't effectively launch their attacking game.
But the Lions might be fixating on this idea that the All Blacks can be beaten up - dominated at the set piece and collisions and sent into a spiral of panic where none of their magic tricks can work.
Whether the Lions are cognitive of it or not, they are giving off clear signals that the true intention of their New Zealand mission is to try to contain and subdue the All Blacks.
They aren't going to try to match them, to deliver that same instinctive, spontaneous style of football. Instead, just like the men of 2005, they are going to be all about confrontation and directness.
It's not a bad plan. It shouldn't, however, be their only plan because just as the likes of Maro Itoje, Courtney Lawes and Toby Faletau are improved versions of their 2005 predecessors, so too are Brodie Retallick, Sam Whitelock and Kieran Read.
Physical domination didn't work 12 years ago. Maybe it will this time but it seems more likely it will highlight to the best players in the Northern Hemisphere that skill development has gone to a new level in this part of the world.
The All Blacks have shown they can make their game work in the most intense physical battles. They can be blitzed on defence and yet somehow still find a way to play the ball into space.
Even when they are under pressure in those contact zones, they are still able to generate pace and width in their attacks, because there is another truism likely to become apparent.
Just as Johnny Sexton, Elliot Daly and Jonathan Joseph are coming with more bells and whistles than their equivalents of 12 years ago, they will encounter men such as Beauden Barrett, Ben Smith, Israel Dagg and Aaron Smith who are equally improved from their 2005 predecessors.
The Lions, it seems, just can't catch up. They move their game on one step, the All Blacks do it by two. Warren Gatland tacitly acknowledged as much during the week when he said: "My biggest challenge for these players is that the ones who have toured New Zealand before, is trying to make them understand what's going to be thrown at them.
"I don't think our Lions players will have experienced the amount of emotion and desire that these New Zealand players are going to bring, it's a once-in-a lifetime opportunity to play the Lions, and create something special, and create history.
That's a big job for me to communicate and prepare these players for the challenges that they will face against some real quality opposition."
