Manager Alan Knill admits Scunthorpe's shock hammering of npower Championship leaders QPR is only the start of the hard work needed to salvage survival.
The home side came from behind to halt a run of five successive defeats and give Knill his first win in charge of the club.
"This was a massive win for us," he said. "After last week's 6-0 defeat at Norwich the first thing I wanted from my team today was a performance."
He added: "I wanted to see them more like the Scunthorpe teams I have always known, full of energy and making life difficult for the opposition. I have to confess I thought 'here we go again' when Rangers opened the scoring.
"But it shows great character from my team that we came back in to the game and beat the team that has been the best in our league all season.
"We are still in a difficult position and we've got a big match coming up against Reading on Tuesday night where we need another big performance."
It was a stunning defeat for the London side, who faded dramatically in the second half after dominating much of the opening period. Striker Rob Hulse headed them in front after just seven minutes, popping up unmarked on the edge of the six-yard box to convert a cross from Wayne Routledge.
Rangers were left to rue missed chances when Scunthorpe suddenly equalised out of the blue in the 28th minute as striker Joe Garner headed home a free-kick from Michael O'Connor.
Garner, on loan from Nottingham Forest, struck again four minutes into the second half, scrambling the ball home from close range before O'Connor and Mark Duffy finished the job.
"It was one of those days that sometimes happens in football," said philosophical Rangers boss Neil Warnock. "It was a game that we could and should have won. We were much the better team for the first half. We got an early goal and if we had got a second I am sure it would have killed Scunthorpe off."
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