The Millers were hammered 4-0 by the Shrimpers who climbed to third, and now Scott's men start a tough programme of games.
Ahead of a trip to Port Vale this weekend, and with league games against Burton, Shrewsbury and Morecambe all to come, the boss says it's going to be a real test.
“It will be a test of character and we’re going to find out who’s got the guts now,” said Scott.
“It will become very clear, very soon, who wants to become part of this and part of what we’re building here. We can, and we will, be successful. So who wants it?.
“I have always been a manager whose teams are organised, who makes them hard to beat, but I was disappointed and frustrated because we work on a lot things defensively,” he said.
“Maybe some players have had too much credit for what they can do rather than what they can’t do. Certainly if they continually do the same things then it’s not going to be right for the football club and you have to pass people by. We have some good players here. But we do need to be more ruthless, harder to beat".
Scotty added; "There’s no point having good players if they’re not going work and do the nasty things like winning headers and blocking shots.
“People want to see us grafting for each other. They (the fans) did not get their moneysworth on Saturday and I do not accept that.”