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The 26-year-old's men's doubles world ranking has skyrocketed 55 places to No18.
He defended his Japan Open title, a week after winning the Shenzhen Open in China.
Topping that was a dream run to the semifinals at the Australian Open, followed by a quarterfinal appearance at Wimbledon.
Not bad for someone who was a "50-50" chance of making the Australian Open draw.
"It's been an awesome year," he said.
"It's been a lot of fun because it's all been new tournaments for me, all the big tournaments and stuff.
"Then just being able to compete and practise and be in that environment has been huge for my development as well.
"I'm happy with the results and the way I've ended the year."
It was that run at the Australian Open which set the tone for the year.
Alongside Jan-Lennard Struff - whom he was partnering for the first time - he hit a run of form and they knocked off the No1 seeds on the way to the semifinals.
His ranking jumped from 73 to 36, meaning he could enter any tournament he wanted.
It also spurred a switch in mindset.
"It was pretty huge for my belief."
So, too, was the Tokyo win last year.
"That was my first tour event.
"Then going on to play my first grand slam and making the semifinals - it was massive for my confidence going forward, knowing that if I played my best tennis I could always compete with the top guys."
His partnership with Struff - a tall hard-hitting German - has proved a winner.
The duo played together in all four grand slams and are planning to do the same in 2019.
"We combine really well and we get along really well, which is awesome.
"It's a lot of fun playing together. The chemistry's there, the game style and everything's there, so we're hoping we'll keep improving together next year," McLachlan said.
That begins with Auckland's ASB Classic next month.
While McLachlan now represents Japan, Queenstown remains home and he is excited to play in New Zealand.
It will be his first time in the main draw in Auckland and he was hoping for a good performance in the lead-in to the Australian Open.
As he enters the grand slam for the second time, he will have a different mindset to the first.
"Last year I didn't have any expectations, really.
"This year I'm hoping to do just as well, maybe even better.
"Maybe there's a little bit more pressure, but I play every week. Every week's an opportunity and I try to treat it like that."
After having a couple of weeks off relaxing and catching up with friends, he was now back into training.
More big goals have been set for 2019.
His major goal with Struff is to make the world tour finals in London.
To do that the duo will have to be in the top eight pairings in the world.
He also hopes to break into the world top 10, while also continuing to develop and set the platform for a long career.