The Dutch international picked up the injury after a collision with teammate Mike Williamson during Newcastle’s 3-0 defeat to Everton on Tuesday evening.
Krul has been a Premier League ever present for the Geordies this season, is now set to miss the fixtures against Southampton, Manchester United and Stoke.
Rob Elliot is is set to deputise between the sticks, and Toon boss Alan Pardew insists he will be an able deputy.
“He’s made the Republic of Ireland squad and is keen to stay in it so he need s to play,” said Pardew, who has completed his three-match stadium ban, but is still unable to watch his side’s next four games from the dug-out.
“The opportunity lands at his feet and Rob’s a confident goalie who’ll look to take that on.”
Pardew is also without top scorer Loic Remy for the game with the Saints this weekend, and must decide whether to persist with loan signing Luuk de Jong or start Hatem Ben Arfa.
“Luuk is coming from a situation where it has not gone well for him in Germany and he is finding his feet and his confidence,” he added.
“I think he has had some good displays but there’s more to come.
“I hope between now and the end of the season, he shows that to our fans.
“We know at this club that we need strikers and I’m hoping he can tick a box for us.
“But it is important his all-round game improves from where he is right now.”