The last two months for Rovers have been characterised by sloppy, poor performances that have seen them slide into the bottom half of League One.
Peterborough - managed by ex-Rovers boss Darren Ferguson - are one win away from promotion to the Championship and boast the division’s best home record.
Butler says Rovers can expect a very difficult night if they are not close to their best at London Road.
“Peterborough are an excellent side and it only takes one player to switch off and you’re in massive trouble,” he said.
“We have to go there with a mindset that we know our roles and responsibilities and we know it’s going to be a tough game from the first minutes.”
Despite a run of nine defeats from their last 12 matches, there is still a mathematical possibility that Rovers could still finish inside the top six.
But anything other than a victory tonight will finally put their hopes to bed.
Rovers have lost only one of their last ten visits to London Road and triumphed 3-0 in the fixture last season.
“We seem to do well against Peterborough so let’s hope we can go there and continue it,” Butler said.
“It’d be nice to keep the play-offs alive for ourselves.
“We’ll keep fighting and there always has to be motivation to keep fighting.”
Butler revealed his gratitude towards Ferguson, who he worked under during the Scottish boss’ time in charge at the Keepmoat, and said he has taken plenty from his former manager as he has forged his own coaching career.
“I think Darren has been excellent,” Butler said.
“I think he was one of my better coaches if I’m being totally honest. He actually improved me as a player and I thank him and Strachs [Gavin Strachan, former Rovers assistant] for everything they did for me while they were here.
“The way him and Strachs went about the finer details and really nailing down what they wanted from different shapes and formations was brilliant.”