George Gregan's career as a benchwarmer is destined to be short lived after a stunning cameo display in the ACT Brumbies 50-18 thrashing of the Highlanders at Canberra Stadium.

The decision to start Gregan off the bench was just one of the intriguing elements of the home side's build-up with the shadow of the axing of coach David Nucifora hanging over the match.

Gregan's benching was a planned move to give Matt Henjak more game time, but the Australian No.9's influence over the final 25 minutes will ensure his starting spot is safe for as long as he wants it.

Despite holding a 29-13 half-time lead, the Brumbies lost their way in the second half and the Highlanders piled on the pressure.

The first ten minutes after the break were spent deep inside ACT territory and only some stout defence and inept Highlanders attack prevented the margin from closing.

Needing something to spark the team, Gregan was injected into the contest in the 55th minute, and his impact was immediate.

With their attack instantly clicking into gear, No.8 Scott Fava reaped the rewards just a minute later, powering into open space to put the Brumbies ahead 36-13.

"George was a bit of a super sub and he really changed the game," Nucifora said.

"We had a bit of a chat through the headset before he went on the field, and he went straight out and did everything I asked him to do."

The Highlanders had their chances at the start of each half to establish dominance, but both times failed to follow through on bright openings.

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