The Brumbies are at risk of being pushed off the top of the Australian conference after a 40-15 loss to the Blues.
The Canberra side held the slimmest of advantages over the Waratahs coming into the match, on the same points as their northern rivals but one extra win kept them on top.
After Friday night’s result, which took the Brumbies' winless streak against Kiwi sides to four, the Waratahs need just a losing bonus point against the Hurricanes in Sydney to snatch the conference lead with their own visit to Auckland remaining.
Five tries were scored in the opening 21 minutes at Eden Park, with four of those going to the home side in an early frenzy.
It took less than four minutes for the Blues to score, with a cross-field kick collected by Jerome Kaino, with no Brumbies in sight, sending the flanker over.
Three minutes later, captain James Parsons finished off a set lineout move in what was a disastrous start for the Brumbies.
It took the ACT just one lineout to return the favour, with captain Stephen Moore driving a maul just short of the line, ultimately awarded a penalty try, with Kaino yellow-carded in the process.
Having a man down didn’t seem to affect the Blues, with Sam Prattley and Matt Duffie crossing for two tries while Kaino was spectating and giving them a 21-point buffer in as many minutes.
Matt Toomua finally added to the Brumbies score 15 minutes later, but couldn’t convert his own score after taking over kicking duties with Christian Lealiifano off under the blood rule.
A series of penalties to the Brumbies gave Lealiifano a chance for three points after the half-time hooter, narrowing the margin to 13 points.
Kaino had his second in the 44th minute to extend the Blues lead, breaking away from the back of a driving maul to score.
A 68th minute try to Blues replacement Matt Vaega was disallowed after winger Matt Duffie scraped into touch as he sent the final pass, before the latter earned a redemptive five-pointer to stretch the lead to 25 points.
The Brumbies were dealt a major blow in the 54th minute with Scott Fardy forced off after a head clash with teammate Jarrad Butler, leaving Michael Wells and Tom Staniforth to back up Butler in the backrow.
(Tries: Kaino 2, Duffie 2 Parsons, Prattley Cons: Francis 5)
(Tries: Penalty, Toomua Cons: Lealiifano Pens: Lealiifano)