The ACT Brumbies captain deserved a fairytale finish to his Super Rugby career after 12 years of service, 150 games and a battle to beat leukaemia.

Brumbies players describe him as the "heartbeat" of the club and he didn't deserve to finish his milestone game on the wrong side of a 39-7 thumping.

Sport, though, is a cruel mistress. The Brumbies never had a chance against the Argentina Jaguares, even though Lealiifano was trying until the very end.

The loss will leave a sour taste in the veteran's mouth as he prepares to move to Japan next season. But it shouldn't, because the fact he was playing was remarkable by itself.

Lealiifano was diagnosed with leukaemia in 2016 and was told he may never play rugby again. Even at his lowest moments he wore a smile around his Brumbies teammates.

His legacy won't be the championship one he craved. But it will be about loyalty, determination, family and fight. The Brumbies will miss him dearly when he leaves, and not just because he's back to his best form.

They will miss him because he was the link between old and new players from different backgrounds and cultures.

The Jaguares were far too good for the Brumbies, there's no doubt about that. But a disastrous error in the fourth minute summed up the Brumbies night.

The Jaguares put a kick over the top in hope more than anything and three Brumbies players - Joe Powell, Rob Valetini and Toni Pulu - converged in attempt to clean it up.

A second of hesitation saw the ball fall between all three, hitting one of their boots and tumbling towards the try line.

Former Brumby Tomas Cubelli won the race to get the loose ball and scored the first try of the game.

It was all downhill from there and being slightly off the pace was the way the Brumbies played the rest of the game.

It would be easy to pile on the Brumbies after their biggest loss of the season, but the weight of 732 Test caps in the Jaguares side was just too powerful.

Lealiifano, David Pocock, Henry Speight, Sam Carter and Rory Arnold have all played their last games for the Brumbies.

Josh Mann-Rea, Chance Peni, Jordan Jackson-Hope and Ben Hyne are leaving as well.

It's a significant changing of the guard. The club's most recognisable players won't be there next season and will leave a gaping hole in experience and leadership.

There will be a new captain, with Lachlan McCaffrey, Allan Alaalatoa or Joe Powell the early options.

Someone will have to step up in the second row and a young gun will likely get a shot at Lealiifano's flyhalf role. The Brumbies are about to walk into the unknown.

No one in the Brumbies' side used the semi-final as a platform to win Wallabies selection. But surely Test coach Michael Cheika cannot overlook their end-of-season form.

Folau Faingaa is considered the front-runner to be the Wallabies' first-choice hooker for the World Cup. He had an off night at lineout time, losing five of his first seven throws under massive pressure from the Jaguares.

Some throws were off the mark, others were just pinched by smart Jaguares jumpers. Either way Faingaa will still be in the mix for Test duties and hopefully the semi-final hasn't damaged his confidence.

Lealiifano has been the form playmaker in Australia this season, however Cheika has been reluctant to pick him in squad since his recovery from leukaemia.

Henry Speight, Tevita Kuridrani, Joe Powell, James Slipper and Sam Carter all did their best to try to earn Wallabies recalls on the Brumbies' seven-game winning streak.

Scott Sio, Allan Alaalatoa and Rory Arnold will definitely be there, while Toni Pulu, Lachlan McCaffrey, Pete Samu, Rob Valetini and Tom Banks are all in contention.