Another victory for Jim Mallinder's side could leave Edinburgh languishing at the bottom of the table with their chances of qualification hanging by a thread.
And Moffat is demanding the Gunners must not only beat Saints, but start picking up victories away from Murrayfield, in order to save their ailing campaign.
"It's definitely a must-win game against Northampton," said Moffat. "We played pretty well last weekend but lost by a point so we have to win on Saturday.
"We don't want to be looked upon as brave losers - We want to be winners and that's what it's about this week.
"We won our home games last year and that's what we have to do.
"We also have to win one or two away to qualify this time around but the players have that
Moffat makes one change to his starting XV which lost at Cardiff City Stadium as James King replaces Alex Grove at inside centre, while Mallinder's Saints remain unchanged.
Glasgow Warriors travel to Wasps on Sunday, looking to build-on last week's 21-13 triumph over Newport Gwent Dragons in Pool 6.