Aaron Hughes has been ruled out of Northern Ireland's final two World Cup qualifiers this week, and would be a doubt were they to make the play-offs next month.
The 108-cap defender has been forced to withdraw from the squad for his country's games with Germany and Norway due to a calf complaint that forced him off seven minutes into Hearts' loss to Dundee at the weekend.
Hughes is one appearance short of becoming the home nations' most capped defender ever, a record he currently holds with Bobby Moore, but manager Michael O'Neill concedes he may also miss the play-offs were Northern Ireland to reach them.
Northern Ireland have guaranteed second place in Group C but only eight of the nine group runners-up will be in November's play-offs.
At 37, that could conceivably mean Hughes has played his final game for his country if O’Neill’s side do not make it to Russia and he decides to call it a day.
Asked if Hughes would be back in time for the play-offs, O’Neill replied: “It’s difficult to tell. I think you have to digest the whole scan when he goes back to his club.
"It's not really our responsibility to get him fit, Hearts want him fit as well. He certainly would come into the doubtful category I would say.
“We’re hopeful that won’t be the case but it may well be that within four weeks, he would probably be right on the edge if he was to make it.
“We feared the worst but Aaron being Aaron travelled as normal. Most players in that scenario would just pull out but he travelled and had a scan on Monday and it showed something wasn’t right.
“It’s a big blow to us because we’re light in that department with Craig [Cathcart] injured and Gareth [McAuley] just back from his injury.”
Hughes had appeared in his country’s past three qualifiers, during which time they did not concede, and he has also featured in both of Northern Ireland’s games against Germany over the past 16 months.
Beyond West Brom duo McAuley and Jonny Evans, O'Neill's only obvious central-defensive options are the trio of Tom Flanagan, Adam Thompson and Callum Morris – none of whom have made a competitive appearance for their country.
McAuley, also 37, has played just 62 minutes of senior football for the Baggies since aggravating a thigh problem against Azerbaijan in June.
“It’s not ideal, we’d rather he played in that scenario,” O’Neill added.
“He’s fit, which is important, he’s in good form, trained well, you can see he’s hungry to play. We need him to play.
“Gareth has all the experience and attitude to come in and play in a game of this nature.
“There are certain players you think can deal with that scenario and get through a game in this type of situation, coming into it with a lack of first-team minutes and I think Gareth comes into that category.
“The other two lads who play at centre-back [Flanagan and Thompson], neither have been playing regular first-team football with their clubs.
“That’s the scenario we’re faced with and we need Gareth to play and he’s very positive and eager to play.”