But it was the Brumbies, deprived of Wallabies Ben Alexander, Dan Palmer, Stephen Moore, Ben Mowen, Christian Lealiifano and Pat McCabe, with David Pocock, George Smith and Joe Tomane also missing through injury, who secured the well-deserved win.
And for Best, skipper on the evening, it was a chastening game as the Lions lineout fell apart, regularly costing them field position in the first half.
He said: "We got physically beaten up, a bit nervy and all the credit to the Brumbies, they were hungrier than us right across the board.
"I don't think we're looking for an excuse, we brought in quality players and we had a quality team. We just got beaten up at the breakdown tonight.
"If you can't secure that ball you're always going to be under pressure. I think the forwards should stand up and take the heat and deservedly so.
"I think we went in fresh, we had a good team run yesterday and were feeling very confident. We knew it was going to be a tough task but we just didn't turn up tonight. Right from the very off they wanted it more. You have to give them massive credit for the way they played."
After an early Lions incursion into Brumbies territory, it was the hosts who opened the scoring in Canberra, Tevita Kuridrani grabbing the first try.
Andrew Smith held his pass just long enough to draw in Stuart Hogg to help Wade, and the Brumbies centre then found Kuridrani outside, the 22-year-old showing all his power to crash over.
The Brumbies should have been further clear in the first half, but a missed conversion, followed by missed penalties from Jesse Mogg and Ian Prior, meant that they were just 5-0 up shortly before the break.
Mogg finally slotted their first kick of the half with a penalty, but the Lions responded immediately through Stuart Hogg to make it 8-3 at the break.
It was more of the same in the second half with Mogg adding two more penalties, only for the Lions to respond with one from Hogg and two from Saracens replacement Owen Farrell.
But trailing by two points the Lions seemed to stall and the Brumbies were able to relieve the pressure and seal a famous win - the first by an Australian province over the Lions in 42 years.
And having lost their unbeaten record on the tour just four days before the opening Test, Best admits the side need to bounce back quickly.
He added: "We let our standards drop tonight and it'll be up to the 15 and 23 this weekend to raise their game. We didn't want to lose the momentum we gained on this tour. We've done that and now we have to dust ourselves down and go from there."
Lions: Kearney; Wade, Barritt, Twelvetrees, Williams (Zebo, 68); Hogg (Farrell, 59), Youngs (Murray, 59); Grant (Corbisiero, 56), Best (Hibbard, 56), Stevens (Cole, 56), Gray, Evans (Parling, 59), O'Brien (Lydiate, 56), Tipuric, Faletau
Brumbies: Mogg; Speight, Kuridrani, Smith A (Holmes, 75), Rathbone (Coleman, 71); Toomua, Prior; Sio, Siliva (Mann-Rea, 56), Smith R, Power (Oosthuizen, 75), Carter (Smiler, 67), Fardy, Faingaa, Kimlin
Scorers
Brumbies
Tries: Kuridrani
Penalties: Mogg (3)
Lions
Penalties: Hogg (2), Farrell (2)
Referee: Jerome Garces
Attendance: 21,655
