The Millers slipped to their seventh home defeat of the season last week when they went down 3-1 to rock-bottom Bristol Rovers, which came hot on the heels of another dismal display in a 2-0 loss to Barnet.
Those results have seen Evans' men slip down to ninth in League Two, though they remain only three points off the top three.
The Cobblers travel to South Yorkshire at the weekend with five wins from their last seven games and Evans hopes the challenge will bring the best out of his side.
"It's a great chance to respond," Evans said.
"Northampton are the form team in League Two, they will be the biggest team that supporters see this season in terms of bulk and size, they are very direct, they get the ball into the box at every opportunity, so we know what to expect.
"It's about what we do, though, if we don't perform we will have no chance of winning."