The tour itself may have started over a week ago, but the Queensland Reds landed the first punch on Australia's behalf during a grueling match on Saturday morning in Brisbane.
The Lions had things all their own way in the opening two fixtures, but the Reds dragged them into the trenches and really made them work for their 22-12 victory.
Now the Lions will enter uncharted territory and take on a scratch team comprised of professional and amateur stars from both New South Wales Country and Queensland Country.
With 10 amateurs in the 23-man squad, and just nine players with Super Rugby experience, many view this game as an easy outing for the Lions.
A quick look at the side the Lions have named shows, while they're taking the game seriously, there is room for experimentation.
When the teams take the field Tuesday, Lewie Catt, an electrical engineer from Newcastle, will be tasked with marking one of the greatest 13s of all time. George North will find himself opposite an apprentice plumber.
These are just two of the many mismatches the Lions will face when they line out in Hunter Stadium, Newcastle on Tuesday night.
But this is one of the beauties of a Lions tour—the chance for these types of players to enjoy the biggest day of their careers.
The bookies, including William Hill, have the Lions as 77-point favourites, and they rarely gets things that wrong.
Some of the professionals that fill out the squad are journeymen like captain Tim Davidson of the Melbourne Rebels, while others like Phoenix Battye are youngsters itching for a chance at the highest level.
They have nothing to lose and will throw everything at the Lions. The Lions' main concern will be the amateurs go head-hunting, looking to add a famous name to their hit list.
Few saw that as a realistic option, but Hogg will find himself at 10 for the first time since he was a schoolboy.
It's a bold move, because a poor performance could kill the young man's confidence, and the Lions have no viable substitute on the bench.
In a certain win, there is little chance a bad game would result in defeat, so the Lions are obviously taking the opportunity to rest Owen Farrell and Jonny Sexton.
Sean O'Brien and Justin Tipuric
The battle for the back row is getting hotter with each passing week. Sam Warburton returned to action over the weekend with a solid, if unspectacular, performance.
Tuesday, two of his main rivals for the role will line up on opposite flanks. The fact that Sean O'Brien now finds himself at six shows the coaches are still debating their best team.
If O'Brien continues in his rich vein of form, he could find himself in the test team on the blindside with Warburton or Justin Tipuric on the openside.
Or Tipuric may turn in another star turn and push Warburton onto the blindside. This battle could go any number of ways.
One gets the feeling that the coaches are giving Richie Gray every possible chance to play his way into form, and thus into the test side.
He offers a unique blend of size and athleticism that is unmatched in the squad but is being comprehensively outplayed by a number of his rivals.
A big performance in the loose Tuesday could push him back into contention, but another quiet game will see his chances fade.
Alongside him, Ian Evans is facing a similar make-or-break outing, but he doesn't offer anywhere near the quality of Gray at his best.
Weeks ago he was preparing to face the Pumas in Argentina, now he finds himself one big performance away from the matchday squad for the first test.
The injuries to Gethin Jenkins and Cian Healy have left Mako Vunipola as the sole loosehead prop left from the original squad.
With Vunipola seemingly have done enough to deserve his place in the test team, there is a spot on the bench which will come down to Alex Corbisiero and his fellow new arrival Ryan Grant.
Corbisiero is given the opportunity to start and will be hoping to showcase his destructive scrummaging.
One of the star turns in Saturday's game came from the talented young Englishman Ben Youngs. With Phillips surely a shoe-in for the test team, Youngs showcased his ability to change a game off the bench.
He will bring a great change of pace to the Lions' task, forcing Australia to prepare for two totally different types of threats. His try was fortuitous, but it was well deserved for his all-round performance. He kept the physical Reds back row honest, freeing up space for those outside him.
Of interest was how much more comfortable Owen Farrell looked outside him. His ability to bring the best out of his English teammate adds to his value.
He's very much the small name of the battle for the Lions' second row, but he is currently making a massive case for his inclusion.
There are a host of big names competing with him for the job, but Geoff Parling is letting his play do the talking. He was imperious in the lineout, stealing four of the Reds' throws while remaining perfect when the ball came his way.
He doesn't have the power or athleticism of some of his rivals, but he hits more than his share of rucks and tackles himself to a standstill.
While Tommy Bowe, before his injury, and George North were cutting huge holes in the Reds' back line, Alex Cuthbert had a night to forget.
Put away in space by Bowe early in the first half, he failed to beat Luke Morahan in the corner and found himself bundled into touch. Morahan then showed him how it was done, leaving Cuthbert grasping at straws as he raced away to score one of the tries of the season.
Bowe's injury means he still has a great chance of starting the first test, but he can't afford another off day.
With such great competition for both centre berths, Jonathan Davies needs a big performance to keep himself in the mix for the test team.
He was solid without standing out, and his chances are surely all but over. He just doesn't offer the individual skills of his rivals. He wasn't helped by the early injury to Manu Tuilagi that saw North come on in the centre, and then later the injury to Bowe that forced further changes.
He never got a chance to showcase his passing, while he butchered a certain try when he over-cooked a kick through off a loose Quade Cooper pass.
Less than a week ago, I mentioned how the Lions had been blessed regarding injuries. For the first time in recent memory there was no pre-tour withdrawals and all players made it through the initial training injury-free.
Now just a few short days later, players have begun to succumb to the rigours of a hard season.
Thankfully they had two able replacements to call on, in the form of Scotland's Ryan Grant and England's Alex Corbisiero.
In the bruising affair at the Suncorp Stadium, there were a few more worrisome sights. First, powerful centre Manu Tuilagi had to be replaced after suffering a shoulder injury. Thankfully, it was not as serious as first thought, Gatland confirming he had merely suffered a "stinger," according to Mick Cleary of The Telegraph.
More worrying is the news that Tommy Bowe's tour may be over. With Alex Cuthbert having a poor game, it looked like Bowe was locking down a position in the test team before disaster struck.
Such is his value to the Lions that he will stay with the squad, despite needing surgery to insert a plate into his hand, in the hopes he will be available for selection in the coming weeks.
Just in case he is unable to continue, the Lions have called up Ireland's Simon Zebo as a precaution.