The Brumbies learnt some harsh lessons about what it takes to be a Super 14 top dog as they lost 50-32 to the Bulls in Pretoria despite encouraging season debuts from stars Matt Giteau and Rocky Elsom.

The visitors led 15-6 in the first half and 27-20 in the second, before the defending champions piled on 30 successive points.

Converted tries in a four-minute period to winger Gerhard van den Heever and centre Wynand Olivier mid-way through the second half signalled an irreversible momentum shift.

Touted as a genuine title contender, the Brumbies scored three tries but were let down by poor discipline, which also surfaced in their first round win over the Force.

They conceded seven penalties in a 16-minute period when they led by seven early in the second half.

Springboks five-eighth Morne Steyn bagged 35 points, scoring two of the Bulls' five tries - all of which he converted - plus five penalties.

"We showed a lack of discipline and a lack to find the extra effort and they showed why they were the champions because they continued to find that for 80 minutes," coach Andy Friend told AAP.

"They continued to hold their composure and they came over the top of us pretty strongly.

"For us to have that lesson in round two might end up being a great thing."

Friend drew some solace from the displays of prize recruits Elsom and Giteau.

Playing his first game of the year, Wallabies skipper Elsom played the full match and appeared ravenous for action, producing a series of tackle-busting runs.

He scored one of the Brumbies' two first-half tries, smashing through three defenders, and set up a first Super rugby five-pointer in four years for fellow flanker George Smith.

A lively Giteau, returning to the Brumbies after three seasons with the Force, skillfully orchestrated several probing attacks from five-eighth before he was replaced with just under 10 minutes remaining.

"I thought Rocky Elsom playing his first time for the Brumbies was very, very good," Friend said.

"It was lovely to have Matt Giteau back. He showed what a class player he is.

"They were two of the positives to come out of it."

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