Stephen Kenny has suffered his first major injury scare ahead of next month's World Cup qualifiers after John Egan was stretchered off in Sheffield United's latest Premier League defeat.
The Ireland centre half's leg was placed in a brace by medics after he stayed down after executing a block in the dying stages of his team's loss at West Ham.
Egan clutched his foot following the impact and it soon became clear that physios were treating the issue seriously.
Sheffield United boss Chris Wilder did not detail the specific nature of the problem but admitted he was concerned by the possible implications and more should become clear on Tuesday.
"It doesn’t look good does it," said Wilder. "He’s a tough Irish boy so for him to stick his hand up wasn’t a good sign.
"He's on crutches now and that caps a miserable night for us.”
Kenny will be anxiously waiting for updates as Egan is a key part of his plans but has largely been unavailable during the new manager's tenure.
The Corkman missed two games in October after being caught up as a close contact of a Covid case and he then sustained a concussion in the opening minutes of the November friendly with England which ruled him out of the rest of that window.
With his centre half partner Shane Duffy going through a torrid time at Celtic which has already left Kenny with a dilemma, losing Egan ahead of next month's crucial trip to Belgrade would be a disaster.
Ireland take on their likely qualification rivals on March 24 before home games against Luxembourg (competitive) and Qatar (friendly).
Ciaran Clark's return to form at Newcastle has strengthened Kenny's hand but Dara O'Shea has dropped out of the West Brom side while Kevin Long has been starved of game-time at Burnley. Blackburn's Darragh Lenihan is another option.
Promising U-21 centre half Nathan Collins is set for a spell on the sidelines following a weekend setback on Stoke duty.