Steve Bruce admits that his initial fear for club captain Jamaal Lascelles was that the defender had torn his knee ligaments.
Lascelles clashed with Martin Dubravka as the pair kept out Callum Wilson in Newcastle United's 2-1 victory over AFC Bournemouth before the international break.
The defender struggled on before conceding he could no longer continue.
Having left the stadium on crutches, scan results brought relief to the United medics and head coach - showing Lascelles had fractured his tibia, and not damaged his ligaments.
'"That sounds terrible because it's a fracture," Bruce replied when asked if the injury wasn't as bad as first feared.
"But I honestly thought the way his knee was that he had done his cruciates - we all thought ****, is it ligaments?
"But he's got a crack on the outside of his knee. So we hope he'll be back within a month to six weeks."
Newcastle options at centre-back have been plentiful with Bruce able to rely on several players who have come in and impressed.
The head coach saw his defensive back-three finish with Federico Fernandez, Paul Dummett and Ciaran Clark against Bournemouth - and it's the Irishman who is the biggest doubt for Monday's game with Aston Villa.
Having scored the winner against Bournemouth, Clark was included as part of the Republic of Ireland squad but the defender picked up a knock in the 0-0 draw with Denmark.
Bruce watched the game from Dubai, and admits that Clark, United's top goalscorer this season, is 'touch and go' but is hoping to have his the defender in his squad.
"I think he'll be okay. He's not trained today but he'll train on Saturday and Sunday if it comes through he'll be in with a chance.
"He's done great has Ciaran, I'm delighted for him."