Krul twisted his ankle in training before Saturday's 1-0 defeat at West Ham and is poised for a lengthy spell on the sidelines.
Pardew confirmed ahead of Tuesday's trip to Burnley that Krul could be unavailable until the new year.
Captain Fabricio Coloccini could also sit out the trip to Turf Moor as he continues to battle a calf injury, with Pardew left to further rue the absences of Moussa Sissoko and Jack Colback through suspension, while Daryl Janmaat, Mike Williamson and Massadio Haidara are all injury doubts.
He said: "It's critical in terms of the spine of the team: no Tim, no Coloccini, no Moussa, no Jack, who would all start if they were fit.
"We're taking 22 players to Burnley, and three of them are youth-team players.
"But we've been in this position before and we've won because the squad has good strength and I hold no fears going to Burnley.
"They've done terrifically of late and they'll be gunning for us. We respect them but we don't fear them."
Pardew knows that many other top-flight teams are suffering from the same difficulties and believes that the rigorous demands placed on players is having a growing impact on their fitness.
"We're carrying a lot of injuries at the moment, but I think all Premier League teams go through that," he added.
"I think the way we play and the way we train in the Premier League, not just us, is putting more players at risk of injury because we're really at the very edge of the physical capabilities of players.
"On top of that they get taken away on internationals, where we've lost so many players this season."
