The 31-year-old will hope to guide his team to victory over the Jaguares in Buenos Aires later on Friday, booking a first final for the Canberra team since 2013.
It would also delay his valedictory game for the twice champions for another week as he winds down his 12th season before joining the post-World Cup exodus of Australian players to Japan.
Diagnosed with leukaemia after the 2016 season, the 19-test Wallaby never imagined playing another game let alone becoming the most-capped Brumby after record holder Ben Alexander (154).
"I haven't thought about it too much," Lealiifano told Australian media of the milestone game at Jose Amalfitani Stadium.
"Obviously it's really special but I don't really know how to feel or explain it. It's been a hell of a journey and this is just another exciting game.
"It's special but every game after being back is special to me, so this adds to that and I'm still very grateful."
Lealiifano underwent chemotherapy and a bone marrow transplant before returning to the field less than 12 months after his diagnosis, an inspirational story for a sport that has had its share of gloom in Australia.
The cancer interrupted his international career during his peak years but now, on the wrong side of 30, he has returned to the kind of form that won him the last of his 19 Wallabies caps against England in 2016.
Bernard Foley has been Michael Cheika's preferred flyhalf for all but a handful of games during his tenure as Wallabies coach, but Lealiifano's assured performances have put pressure on the New South Wales Waratah ahead of the World Cup in Japan.
Lealiifano played in the Brumbies' 2013 final, a gallant 27-22 defeat away to New Zealand's Waikato Chiefs -- so anything less than the title would feel short of a fairytale finish.
"The fairytale isn't just to get there, it's to win it," he said.
"But for now we're just focused on getting there. It would be nice to finish on a high but there's plenty of work to do between now and then.
"Two more to go."
(Reporting by Ian Ransom in Melbourne; Editing by Sudipto Ganguly)
