Two of the changes were injury enforced. But the other three are both fascinating and brave. However, they are also well-founded and dropping two Welshmen undermines somewhat the theory of those who have suspected him of feather bedding for Wales.
The selection of Tommy Bowe ahead of Alex Cuthbert comes as a welcome surprise to Irish supporters, especially given that Cuthbert scored a good try last Saturday.
Cuthbert, George North and Mike Phillips have been at the heart of Gatland's power play, using big men to ensure gainline success and more. The match against the Queensland Reds, however, was instructive in terms of Bowe's selection.
For in that match Cuthbert was all at sea defensively, being led a merry dance by Quade Cooper. On a couple of occasions Cuthbert jumped out of the line, only to have delicious passes float over him, exposing the team.
Less than a minute after one of these events, Bowe gave a master class in defending a two-on-one, forcing the pass with a little inward dummy while not selling himself, ensuring he was still able to cover the outside man.
In that moment, I believe, he made himself a Test starter only for injury to intervene. In fairness, he also looked very sharp with ball in hand as well. And, he is not exactly a small man either, is he?
The dropping of the other Welsh powerhouse, scrum half Phillips, was, I believe, made almost certain as early as Will Genia's moment of inspiration for Israel Folau's first try after just 13 minutes of the first Test.
It was not the buying of the dummy that did for him, but what happened next. The head-on camera showed it best. Phillips simply stopped running. It was an extraordinary dereliction of duty.
Had he not simply stopped running in a situation which was obviously exceedingly dangerous, there is every chance that he could have assisted in preventing the try being scored.
Whatever was going through his head, it gave the lie to the notion that players would die for the shirt. Had Gatland substituted him right there, he would have been justified. Phillips stayed on the field and went on to give an underwhelming performance all round.
Ben Youngs, meanwhile, gave a timely demonstration of what he is about with a typically sharp try against the Melbourne Rebels and merits the start. As does Conor Murray his place on the bench. Murray once again made a fine contribution on Tuesday and he has had a quietly excellent tour to date.
The third optional decision by Gatland was to replace Tom Croft with Dan Lydiate and bring Sean O'Brien onto the bench. Had Croft not had an absolute blinder against the NSW Waratahs, I think this is the back row he would have gone with.
To me, this is typical Croft. He has everything in the locker to be a world class operator, and once a year or so, he delivers a complete performance that elevates him to that level in people's minds. Then he goes back to being relatively non-descript for a spell.
I feared this is what would happen when he was selected for the first Test and so it has transpired, unfortunately. Lydiate had an effective game on Tuesday, doing what he does, tackle well, and throwing in a nice reverse pass to set up O'Brien in the corner as a bonus.
Having O'Brien on the bench simply reverses what was Gatland's worst decision all tour in omitting him first time out. When the Lions were ceding the initiative in the final quarter last Saturday, he only had the defensively excellent but offensively uninspired Lydiate to call upon.
His back row was struggling to win the gain-line against an outstandingly committed Wallaby defence and O'Brien was absolutely the man he needed at that moment.
With Geoff Parling getting due reward for his lineout excellence all tour iin replacing Paul O'Connell, and Mako Vunipola coming in for the injured Alex Corbisiero, you would have got decent odds on that precise front five representing the Lions on this huge occasion - but it is the best available to Gatland at the moment.
Gatland's other big call was to stand over his preference for Jamie Heaslip over Toby Faletau. The latter surely heaped more pressure on the coach with another solidly impressive display against the Rebels.
As against that, I thought Heaslip had a fine game in the first Test, making a turnover and picking up a lot of loose ball. Speculation over his selection has generally come down to the Lions' inability to convert a five-metre scrum at a key moment, as the ball spilled out and allowed Genia to filch it.
However, close examination shows that the ball never made it as far as Heaslip and the number 8 was blameless in the incident. For my money, Heaslip carries better than Faletau and offers more pace and the potential to deliver a really big play in support of the outside backs.
Johnny Sexton had a fine game in his first Lions Test start, pulling the strings adroitly and finding space with little dinks over the Australian back-line. His call for the move that led to Cuthbert's score was masterful, exposing the cobbled together midfield partnership of Michael Hooper and Pat McCabe.
Brian O'Driscoll was the most frustrated man in world rugby just 13 minutes into a game in which he had already conceded three penalties (and was perhaps lucky not to have faced further sanction for talking back to referee Chris Pollock in the way that he did - 'Just look at the video').
However, he adapted his game well, even if the referee's interpretation of the breakdown denuded him of a key element of his game.
In truth, the referee kept the Wallabies in the game when he allowed them on two occasions to dive in cynically to prevent the Lions scoring a try without brandishing a yellow card.
Had he done so, with the Lions in the ascendancy at that point, I believe they could have come through with a bit to spare. As it is, the Wallabies will feel they are the more likely to improve and have it in them to set up a decider in the third Test.
As with all Australian sides, they are joyous to behold with ball in hand. Genia, Kurtley Beale and Israel Folau are their game breakers and if they can get the latter two involved they certainly have a chance.
Their forwards lost the scrums, but manageably so, and competed very well everywhere else, particularly the back row. It would have been interesting to see Hooper v Sam Warburton develop as the game went on, but that was unfortunately denied to us by the departure of McCabe.
Where Gatland is showing an ability to take on board the evidence in front of him, Robbie Deans remains fixated on the notion that James O'Connor is a test level out-half.
Whatever about the Quade Cooper situation, I cannot understand why he has not got the Brumbies out-half Matt Toomua in the side allowing O'Connor to complete a potentially devastating back-three with Beale and Folau.
Gatland's selection has changed the Lions game-plan somewhat, and the loss of O'Connell is considerable, but these Lions have what it takes. Just. But they will have to do it up front, with Sexton putting them in the right positions and playing territory a little more than last week.