England welcome Samoa to Twickenham on Saturday looking to end a run of five straight defeats, albeit four of those coming against world champions New Zealand.
Samoa's build-up has been disrupted somewhat by reports that players could refuse to play the fixture due to concerns that their union is being mismanaged.
However, despite claims of unrest in the Samoa camp, Lancaster is not taking the challenge lightly, claiming the encounter will be like a "cup final" for England's opponents.
"We're expecting physicality, pride and passion from Samoa," said the England coach. "This game is their cup final. It's a great opportunity for them and they'll be hugely motivated.
"I watched them beat Wales in Cardiff a couple of years ago in a similar fixture. They are very difficult opposition, so we need to be at our best.
"It will be incredibly competitive right from the start. Just look at the Wales versus Fiji game last weekend [which Wales won 17-13], Fiji almost won it.
"We know it's not a game we can take lightly whatsoever because they'll be putting us under pressure."
Lancaster has responded to last weekend's 31-28 defeat to South Africa by making five changes to his starting XV, as he runs the rule over his entire squad ahead of next year's World Cup.
And the 45-year-old has demanded an improved showing.
"Certainly we need to improve the quality of our performance. The players have been told that and we have made changes to create that," he added.
"You get to a point around this time of the week when your work is done and the players have to take the responsibility for delivering."