After scoring 261 points and 33 tries in winning five successive games, the Lions were dealt a major setback as they lost their unbeaten record in the 14-12 loss.
It was the first time they had lost to any provincial team since South African side Northern Transvaal beat them 16 years ago.
The defeat came just four days before the first Test against Australia, when the Lions will set out on the road to a possible first series triumph since 1997.
“We spoke straight after the game, and we’ve got to pick ourselves up straightaway,” Leicester lock Parling said.
“We can’t mope around. This hurts, it hurts like hell, but you can’t start feeling sorry for yourself. There are some massive games around the corner.
“We can’t afford to have our heads down. That is not just with the game at the weekend in mind, but I am thinking as well about the environment and going back to the hotel.
“If people mope around, then that might spread. We just can’t afford to be like that. We have a massive game at the weekend and we need to pick ourselves up and get back on the horse.”
Parling went on as a second-half substitute and played a key part in underpinning a vastly improved display after the Lions suffered a mauling during the first 40 minutes.
“You’d rather we won and kept that run going. You would rather you did not need a reality check,” Parling added. “But if it has come, we’d rather it come tonight and not at the weekend. We got a little bit edgy at the lineout, and we need to come back from this. I would love to be involved at the weekend. After you lose any game the thing you want to do is play again as quickly as possible.”
“You saw their [Brumbies] reaction at the end, you saw what it meant to them on the pitch. We were in the dressing room at the end and their guy came to me and said ‘I could retire now’. It meant that much to them, he said it’s the biggest game he’s ever going to play.
“Listen, we didn’t play well enough, and I thought they were outstanding. They showed a tremendous amount of fight and we just didn’t match it.”
Hooker Rory Best, the Lions captain yesterday, pulled no punches as he assessed his side’s performance, admitting they had been nervy and outfought up front by a Brumbies side that he said showed much more hunger than the tourists.
“We got physically beaten up up front. They put a lot of pressure on the set-piece and we got a bit nervy. All credit to the Brumbies. They were hungrier than us right across the board,” Best said.
Best refused to use the changes made to the Lions XV as a reason for the performance, saying: “I don’t think we’re looking for excuses. We brought in quality players. When you looked across the team we had a quality team.
“We just got beaten up at the breakdown tonight. At this level, if you can’t secure that ball you’re always going to be under pressure.
“The forwards will stand up and take a lot of the heat, and deservedly so.”
The Irishman added: “We let our standards drop tonight and it’ll be up to the 15 and 23 guys picked this weekend to raise those again. Now we have to dust ourselves down and see where we go from here.”