The Warriors entered the contest needing a win to keep their finals ambitions on life support, only for the ruthless Rabbitohs to pull the plug with an 11-try rout of the injury-decimated Kiwi side.
Now placed 14th on the ladder and three wins outside the top eight with six games left, Brown admits a finals berth is now out of their reach.
"I think that [the finals] is starting to look beyond us now, if we are being truthful," Brown says.
"I'd like to say it is not, but you get to a stage where there's only so many games left, and for us we haven't had a win for a while and we lost some more troops today.
"For us it is more about what we did last week. We started to put things in place (against the Panthers) that is going to help us going forward but today I felt we went backwards a little bit.
"We knew coming in today it was going to be a difficult task but I just thought we could have made a better account of ourselves in the early 20 to 30 minutes of the contest."
Already missing several key players - including captain Roger Tuivasa-Sheck - the Warriors' injury woes were compounded by the loss of stand-in skipper and key forward Addin Fonua-Blake during the game to a finger injury.
Jack Murchie and Eliesa Katoa were also forced out of the game with head knocks.
Next week's return of Tuivasa-Sheck, Chanel Harris-Tavita, and Peta Hiku against Wests Tigers offers some relief, although a dangerous tackle charge may come back to haunt forward Matt Lodge.
"We do find ourselves in situations in our defence under pressure that is not quite near the level that it needs to be," he notes.
"Unfortunately because we don't defend well enough against that type of quality opposition we didn't wrestle any momentum in the game and the score becomes a little embarrassing.
"We still have an element of players where the good and bad part of our defence is just too far away.
"For us to become the team that we would like to become over the next few years it is certainly an area we need to work hard at as a coaching staff and a playing group."