Holding a 6-5 lead in a third-set tiebreak, all eyes were on the 25-year-old from Queenstown as he and partner Jan-Leppard Struff looked to clinch a spot in the men's doubles semifinals.
Clinch it they did.
After a fault on his first serve, he found his mark.
From there a smash by Struff proved the winner to secure an upset 6-4, 6-7, 7-6 win over the world No1 duo of Lukasz Kubot and Marcelo Melo at Margaret Court Arena.
It was a show of calmness under pressure as world no73 McLachlan continued his dream run.
Indeed it is now hard to believe he had felt he was a 50-50 chance of getting into the draw.
The key moment came in the very first game.
McLachlan and Struff broke the serve of their more favoured counterparts and did not drop a point until the third game.
Kubot and Melo were error-prone early on, while McLachlan and Struff were tidy in everything they did.
However, Kubot and Melo fought back and secured their own break after a long deuce.
McLachlan and Struff negated that straight away though, breaking back to set up a first set win.
Late in that set, McLachlan took a medical timeout, in which he appeared to have his ankle strapped. If it impacted on him, he did not let it show.
Neither side gave anything away from that point on.
Both held their own serves, as Kubot and Melo became more clinical and errors began to creep into McLachlan and Struff's game.
That could have been expected though, as they were forced to hit more winners from the second set onwards.
However, they did what they had to.
Struff demonstrated power throughout, while McLachlan showed his quick reactions close in to the net.
With nothing splitting the duos at the end of the second set, the favourites pulled one back to win the tiebreak.
It had stayed even at 4-4, before Kubot and elo finished the stronger to claim the second set.
The third set was similarly tense, nothing splitting either pair.
It was a backhand from Struff which proved the tiebreak's defining moment.
With the score at 3-2, he split his opponents down the middle on a return, taking a crucial point against the serve.
From there they held their nerve, McLachlan hitting the key winner to take it to 6-3, before serving for the win at 6-5.
