Knowing that the Wallabies are likely to get better as the series goes on, while the exploits of a long season begin to wear on the Lions, victory this weekend is paramount.
With momentum on their side the Lions have not rested on their laurels, making five changes from the side that started the first test.
The Wallabies themselves have been forced into a number of changes, meaning both sides' preparations will have changed from last weekend.
A big part of Gatland's tactics through the years is the ability to punch holes in close to the breakdown. This sucks in defenders, creating mismatches out wide and giving his powerful backs space to exploit. But last weekend the Lions were dominated in the trenches.
Time after time Lions ball-carriers were met with a yellow wall in defence. This inability to break the gain-line starved the Lions backs of quick ball.
Looking at the Lions selection, they have done very little to rectify the situation. Dan Lydiate, who comes into the back row at the expense of Tom Croft, offers very little in the way of a ball-carrying threat.
What he will do is hit more rucks than Croft, which should speed up the ball coming back to Ben Youngs, and keeping his opposite number, Ben Mowen, from having free reign to cause havoc.
If the Lions are to do damage out wide they will need to supply the back division with quicker ball, either through smashing over the gain line or cleaner rucking.
While a huge emphasis will be placed on Mako Vunipola, who will have his hands full in the set piece, the Lions at least have the option to spring Croft and Sean O'Brien off the bench.
When Vunipola came off the bench after 50 minutes of the first test, we saw exactly why Alex Corbisiero was selected ahead of him.
Up to that point, the Lions scrum had been secure, if not slightly dominant. But the dual introduction of Vunipola and Dan Cole turned the tide in Australia's favour.
Suddenly a point of attack became an area of weakness. Twice in the last few minutes the scrum disintegrated, once to allow the Wallabies to break out of defence and another time to give them a potential game-winning shot at goal.
The last scrum failure was caused by a slip rather than a system failure, but the first scrum collapse was a worry going forward.
Secure ball would've given the Lions a chance to close out the game, if not secure a score to put them out of Australia's reach.
If Vunipola replicates his cameo, the Lions will be in trouble, but let's hope he has learned to scrum in the last week.
While the Lions lineout was perfect on their own throw in the first test, it provided very little in the way of attacking ball.
The only time the Lions did attack off the lineout ball it was through a driving maul, a maul the Wallabies pulled down to give Leigh Halfpenny an easy shot at goal.
Time after time, the Wallabies gave up the front of the lineout. This gave the Lions secure ball but allowed the Wallabies to fan out in defence, limiting the space out wide.
Dropping Tom Croft in favour of Dan Lydiate robs the Lions of a potential outlet at the back, though Jamie Heaslip has filled that role for Ireland in the past.
With Tom Youngs seeming comfortable hitting his men the Lions need to take a few risks, especially in Australian territory, and throw the ball to the tail.
The first test was a tale of two contrasting scrum halves. Where Mike Phillips was slow and ponderous, Will Genia gave a masterclass in game management.
With James O'Connor struggling to impose himself, Genia dictated everything the Wallabies did with the ball.
He kicked brilliantly, while Phillips' work with the boot was very loose. He showcased his eye for a gap, highlighted by his break and intelligent kick in the build-up to Israel Folau's first try.
Phillips, for his part. was living off slow ruck ball, but even then his delivery was slow and gave no space to the men outside him.
Gatland has shown a ruthless streak by dropping Phillips from the matchday 23, replacing him with the effervescent Youngs.
At his best, Young is almost unplayable. With a quick delivery and searing pace, he offers a dual threat while allowing Jonny Sexton to dictate the tempo.
The selection of Dan Lydiate will help him hugely, as the Welshman will hit a mountain of rucks and stop Ben Mowen from dominating the contact area.
While Alex Cuthbert's fantastic try last weekend wasn't off first-phase ball, it showcased just how deadly the Lions can be when they get clean ball.
All throughout the tour this has been a staple of the Lions' play. They sent big powerful ball-carriers through gaps, and if they fail to score themselves, there are players running in support to finish off the attack.
Of course, the fact that openside flanker Matt Hooper was filling in at 12 made it easier, but it was a fantastic showcase of set-piece rugby.
With quick ball the Lions are very adventurous. They run a host of intelligent decoy lines, sucking in defenders, and in Jonny Sexton have a player with the vision to pick the right option.
If the Lions scrum holds up and they can hit the tail of the lineout, expect more of this style of play.
Brian O'Driscoll's intelligent running, both as a decoy and in support, is key, but it will be down to Sexton to see the gaps and for the strike runners to hit those holes.
If they can, the Lions can do some serious damage. With the Wallabies looking more dangerous off loose ball, this sort of ball could be the key to a Lions victory.