Stubborn defence and a brilliant late try booked the Waratahs a home final in Sydney next weekend by beating the Brumbies 26-8.
After the dominance of the Crusaders earlier in the day against the Sharks, watching the 'Tahs and Brumbies batter each other into the mud will have given Richie McCaw and co. something to smile about. They will get a hell of a contest.
This was less of the beautiful backline play we've come to expect from the Waratahs this season and more a brutal slog, typical of an Aussie derby played out in front of a 38,000 crowd.
Michael Hooper was outstanding. Few 22-year-olds handle the captaincy as well as the Wallaby openside, who flung his rig into the collisions with raw abandon and made turnovers when they mattered most.
The Brumbies insistence on turning down shots at goal at first seemed naive, but by the end was utterly foolish. Doing so on at least four separate occasions yielded one unconverted try - five points when they could have had as many as twelve and forced a tighter finish.
Instead the Waratahs held firm, ahead by more than a converted try and not giving an inch. So much of their play this year has been pretty, but this was the resilience that they will need to defeat the Crusaders next weekend.
In a way it's impressive that the Waratahs have topped the table given the inconsistency of their set-piece.
Tatafu Polota-Nau on this evidence can't be a great darts player, while the Brumbies undoubtedly had the upper hand in the scrum early on.
As the Brumbies faced unrelenting pressure in defence, Alofa Alofa pounced on a loose ball to sprint 60 metres for the game's opening try.
Bernard Foley's three points put the Waratahs 8-0 up at the end of physical opening quarter, dominance in defence overcoming ambition in attack.
Even with plenty of time on the clock and hardly a mountain ahead on the scoreboard, three times from penalties in the Waratahs 22 the Brumbies elected to kick to the corner rather than the posts.
It was a gamble that finally bore fruit, Henry Speight continuing his hot streak with a try in the corner to put the Brumbies on the board after half an hour.
Momentum was slowly creeping the visitors way but just as Lealiifano levelled things up, the Brumbies infringed before the sound of the hooter for Foley to send his side into the break up 11-8.
Lealiifano's kicking was so exemplary in 2013 that his 2014 standard has been shocking. His latest miss, a straightforward attempt near the posts, could have come back to bite the Brumbies.
Kurtley Beale's try saw to that, ripping the ball from the clutches of Jesse Mogg as the Brumbies full-back stuttered, before sprinting away to the corner.
Robbie Coleman was inches and a catch from hitting back for the Brumbies but the ball just wouldn't sit in his hands with the corner ahead of him. The sting of that was worsened by seeing Henry Speight limp off.
Bodies were being pummelled. Nic White suffered the full force of Will Skelton but earned a penalty for his efforts. The option to go for points was again rejected, keeping the Brumbies eight points down at 16-8.
It was the same story minutes later when the Brumbies opted for a scrum, unable to find the try against the side who have conceded the least points in 2014.
Beale's try aside, the Waratahs had barely touched the Brumbies half, but given the nature of their dominance it was no surprise to see them immediately score more points as Foley added his third penalty.
Victory almost assured, the Waratahs capped it with a moment of magic. Breaking out from the back through first Benn Robinson and then Rob Horne via Folau, Will Skelton's run was out of this world.
Palming off would be tacklers the giant had the presence of mind to find Foley for the 'Tahs third try, and one of their best of the year. A fitting end to a dogged performance. The Crusaders are coming.
Tries: Alofa, Beale, Foley
Pens: Foley 3
Yellow Card: Naiyaravoro
Waratahs: 15 Israel Folau, 14 Alofa Alofa, 13 Adam Ashley-Cooper, 12 Kurtley Beale, 11 Rob Horne, 10 Bernard Foley, 9 Nick Phipps, 8 Wycliff Palu, 7 Michael Hooper (capt), 6 Stephen Hoiles, 5 Jacques Potgieter, 4 Kane Douglas, 3 Sekope Kepu, 2 Tatafu Polota-Nau, 1 Benn Robinson.
Replacements: 16 Tola Latu, 17 Paddy Ryan, 18 Jeremy Tilse, 19 Will Skelton, 20 Mitch Chapman, 21 Pat McCutcheon, 22 Brendon McKibbin, 23 Taqele Naiyaravoro
Brumbies: 15 Jesse Mogg, 14 Henry Speight, 13 Tevita Kuridrani, 12 Christian Lealiifano, 11 Robbie Coleman, 10 Matt Toomua, 9 Nic White, 8 Ben Mowen, 7 Jarrad Butler, 6 Scott Fardy, 5 Leon Power, 4 Sam Carter, 3 Ben Alexander, 2 Josh Mann-Rea, 1 Scott Sio.
Replacements: 16 Ruaidhri Murphy, 17 Ruan Smith, 18 Allan Alaalatoa, 19 Fotu Auelua, 20 Tom McVerry, 21 Michael Dowsett, 22 Joe Tomane, 23 Pat McCabe.
Referee: Jaco Peyper
Assistant Referees: Craig Joubert, James Leckie
TMO: George Ayoub