The Waratahs' hopes of making the Super Rugby play-offs are hanging by a thread after they suffered a 34-28 defeat to the Blues at Eden Park on Friday.
A losing bonus point was enough to lift Daryl Gibson's men to the top of the Australian Conference, but the Brumbies now need just a point from their meeting with Western Force - who have won twice all season - on Saturday to retake first place.
There was no shortage of attacking threat from the Tahs in Auckland, the visitors claiming four tries.
However, the Blues were able to respond swiftly on each occasion and the Waratahs only claimed a bonus point courtesy of Piers Francis missing a late conversion.
Three penalty tries were awarded in the match, the Waratahs earning two through dominance at scrum-time, while conceding another when a driving maul was illegally stopped.
Although the Blues trailed twice, they did not give up the lead after Francis stepped off the right to touch down early in the second half, before adding a penalty to put his side eight points clear with 22 minutes remaining.
The Waratahs twice got back to within one point, through converted tries from Israel Folau and former Blues prop Angus Ta'avao, but scores from Melani Nanai and George Moala ensured the enterprising hosts prevailed.
Francis' failure to convert Moala's score means the Brumbies are not certain to extend their season just yet.
The Waratahs have lost with a bonus point. Which means we must get at least a bonus point tomorrow night to make the @SuperRugby finals.— Brumbies (@BrumbiesRugby) July 15, 2016