The Bulls' hopes of making the Super Rugby play-offs were dealt a major blow with a 22-16 loss to the Brumbies in Canberra on Friday.
The result provisionally takes the Brumbies back to the top of the Australian Conference, one point clear of the Waratahs, who must still play the Lions on Saturday.
Two second-half tries from winger Henry Speight handed the Brumbies a crucial win in a three-way battle for a home semi-final berth with the Stormers now also under pressure to get a result over the Cheetahs.
For the Bulls, who are still winless after three games on tour, a losing bonus point falls well short of what they needed.
Highlights were few and far between as the Brumbies led 8-6 at the end of a first half marked by the Bulls' remarkable ability to win turnovers on defence with the hosts camped on their tryline.
Replacement lock Jordan Smiler's try meant the Brumbies were ahead at the interval but the scoreline was by no means a reflection of the opening period, which saw the home side completely dominate both territory and possession.
The game came to life in the second half though as Speight's brace gave the Brumbies a healthy lead, only for the Bulls to come storming back in the final quarter, with a trademark rolling maul try setting up a tense finish.
The Bulls hardly touched the ball in the first quarter, but could nevertheless open a 6-0 lead. Handré Pollard slotted two penalties from long range as the visitors were made to put in a lot of tackles but defended well and picked up points without getting near the Brumbies 22.
The home side's pressure eventually got some reward as Christian Lealiifano slotted three points before David Pocock set up the game's first try for Smiler with an excellent steal and break. With the Bulls back pedaling, Smiler – on after a nasty knee injury to Sam Carter – slipped through the defensive line from close range went over in the corner, but Lealiifano missed the conversion.
Pollard's third penalty briefly put the Bulls in front early in the second half but the Brumbies were soon back on the attack.
The Brumbies have generally struggled in the quarter after the interval this season but they had no such worries as Speight hit the line at pace from first receiver, beat Pollard and Burger Odendaal, before racing 40m to score.
Lealiifano's easy conversion gave the hosts a six-point gap which quickly grew to 13 as Speight was put into space out wide for his second try, which his fly-half converted.
Cue the inevitable Bulls fightback with Lappies Labuschagne scoring from the back of a textbook maul as the game entered the final quarter.
Pollard's conversion brought the visitors within striking distance and although they applied plenty of pressure in the closing stages, the Brumbies defence held firm with Pocock and Jarred Butler making a few crucial steals.
Tries: Smiler, Speight 2
Cons: Lealiifano 2
Pens: Pollard 3
Brumbies: 15 Jesse Mogg, 14 Henry Speight, 13 Tevita Kuridrani, 12 Robbie Coleman, 11 Joe Tomane, 10 Christian Lealiifano, 9 Nic White, 8 Ita Vaea, 7 David Pocock, 6 Scott Fardy, 5 Sam Carter, 4 Rory Arnold, 3 Ben Alexander, 2 Stephen Moore (c), 1 Scott Sio.
Replacements: 16 Josh Mann-Rea, 17 Allan Alaalatoa, 18 Ruan Smith, 19 Jordan Smiler, 20 Jarrad Butler, 21 Michael Dowsett, 22 Nigel Ah Wong, 23 James Dargaville.
Bulls: 15 Jurgen Visser, 14 Francois Hougaard, 13 JJ Engelbrecht, 12 Burger Odendaal, 11 Bjorn Basson, 10 Handré Pollard, 9 Rudy Paige, 8 Pierre Spies (c), 7 Arno Botha, 6 Deon Stegmann, 5 Grant Hattingh, 4 Flip van der Merwe, 3 Marcel van der Merwe, 2 Adriaan Strauss, 1 Dean Greyling.
Replacements: 16 Callie Visagie, 17 Trevor Nyakane, 18 Werner Kruger, 19 Jacques du Plessis, 20 Lappies Labuschagne, 21 Jacques-Louis Potgieter, 22 Travis Ismaiel, 23 Jesse Kriel.
Venue: GIO Stadium, Canberra
Referee: Marius van der Westhuizen
Assistant Referees: Rohan Hoffmann, Ed Martin
TMO: Ian Smith