The Iron are fourth from bottom, one point adrift of safety, but have played two games more than nearest rivals Oldham and Duffy reckons draws will not be enough to keep the club in the third tier.
Brian Laws' side play Leyton Orient at Glanford Park on Friday and Duffy told the club's official website: "It's a massive game for us and we all know that. Matches are running out and we know draws are no good for us.
"We went down to their place in December and picked up all three points, so we can use that as a belief for doing it again this Friday.
"I think we need at least four wins from the remaining seven."
Meanwhile, Scunthorpe have extended teenage Stoke striker James Alabi's loan spell until the end of the season.
Alabi, 18, who scored on his debut against Hartlepool, has so far made four appearances for the Iron.