But Deans and co could so easily have been celebrating a hard-fought victory, after Kurtley Beale twice missed chances to knock over a late penalty at the Suncorp Stadium.
The New Zealander admits defeat was tough to take, particularly as the Wallabies were forced into a trio of significant backline changes inside the first 48 minutes when Christian Lealiifano, Berrick Barnes and Pat McCabe were all stretchered off.
"It was a courageous performance. It would stack up alongside any. On that basis, it's disappointing not to get the reward," said Deans.
"It's very frustrating. I'm proud of the effort the boys put in. It was a trying circumstance and to put themselves in a position to win the game was a good effort.
"It was an epic struggle. It was reasonably slippery under foot so that probably didn't help the pace of the game, but it was an epic contest and either side could have won.
"Obviously we didn't win it so we go to Melbourne now having to win. We came second and we get an opportunity next week."
Bouncing back from the manner of that opening reverse is clearly a big ask but Deans is convinced the host nation have what is required to take the series to a Sydney decider.
Deans insists his team will pose a significant threat if they can maintain possession in Melbourne, especially as he saw nothing that surprised him from the Lions in the opening 80 minutes.
"We have to. I'm not a big one on confidence, it's neither here nor there. We'll have some work to do. We'll assemble a team, go to work and we'll turn up next week," added Deans.
"It was pretty much (what we expected). They're very efficient, they're well drilled and well structured.
"We need to spend a bit longer in possession, we didn't have much ball at all there in the first half - I think it was just one lineout late into the first half. We showed when we did have possession how effective we could be, so that would aid our cause."