It's been a bad 24 hours for Republic of Ireland manager Mick McCarthy.

In the space of a day, or a late night in the case of Richard Keogh, the Ireland boss has lost his two first-choice centre-backs ahead of the most crucial week of the Euro 2020 qualifying campaign.

Both Keogh and Shane Duffy look likely to be absent for next month’s crunch double-header with Georgia and Switzerland.

Keogh’s injury is the more dramatic of the two. The Derby County captain has been ruled out until the end of the season with a serious knee injury sustained in an accident that led to two of his team mates being arrested for drink-driving. A car-crash in every sense of the term.

The Championship club confirmed that Keogh had been involved in an "alcohol-related incident", after drinking into the night following a team-building dinner.

Mason Bennett and Tom Lawrence were arrested and charged the duo with drink driving after a collision. Keogh was a passenger in Lawrence’s car and damaged his knee in the crash.

At the age of 33, questions will now be raised over Keogh’s future as a professional both internationally and at club level and even should he recover in time for the European Championships, should Ireland qualify, his lack of fitness or game-time would surely rule him out of the tournament.

Duffy’s injury is far more mundane and short-term but will still present McCarthy with a big headache.

The Brighton defender picked up a calf injury in his side’s Carabao Cup defeat to Aston Villa on Wednesday night and left the ground on crutches.

It’s still early but his club manager Graham Potter confirmed that Duffy will have a scan today and that it’s looking like he’ll be out for "a number of weeks".

The timing couldn’t be worse for McCarthy who would be able to cope without one of either Keogh or Duffy, but has to come up with some big answers with the pair of them out.

John Egan is the most obvious choice to slot in.

The Sheffield United defender has been in a rich vein of form this season with his newly promoted club and played a starring role in Sunday’s backs-to-the-wall victory over Everton, having featured in every minute of his side’s Premier League campaign thus far.

Egan captained Ireland to a 3-1 victory against Bulgaria early this month and even if McCarthy had a full squad to choose from, the 26-year-old Corkman would be pushing for a starting place against Georgia and Switzerland, with Keogh’s position in the starting XI coming under pressure.

The big question now would appear to be, just who will partner Egan for the double-header?

Kevin Long and Ciaran Clark are the most likely but there’s caveats over both players.

Long has the advantage of having partnered Egan in the heart of defence for Ireland’s last game, that 3-1 friendly over Bulgaria and although it wasn’t the most testing of evenings, he acquitted himself adequately.

Up against a struggling side with just one striker, Long turned in a respectable display and scored his first international goal, offering himself as a threat from dead-balls, which could be crucial away from home in Georgia and Switzerland.

Long’s biggest problem is that he still hasn’t played a minute of league football this season.

While Egan has quickly established himself as a Premier League centre-back, Long remains on the fringes of things at Burnley and his only game-time for his club this season has come in a 3-1 Carabao Cup defeat to League One’s Sunderland.

McCarthy has made no secret of just how important it is for his players to be lining out for their clubs, week-in, week-out. With just 180 minutes of football under his belt this season, in normal circumstances, Long wouldn’t have a chance of featuring in October’s double-header.

It’s an almost identical situation for Ciaran Clark at Newcastle, who has struggled to break into the team under new manager Steve Bruce.

Like Egan, Clark has managed just one game for his club this season, also in the Carabao Cup and he turned in a solid, if unspectacular display in his side’s 1-1 draw with Leicester before they exited the competition on penalties.

There’s very little to chose between Egan and Clark, although the former’s decent performance and goal against Bulgaria could him the slight edge, but it’s far from the position that McCarthy wants to be in going into October.  

The Irish boss may even turn his attentions to Stephen Kenny’s underage side and he has let it be known that he’s been keeping close tabs on the progress of both Dara O'Shea and Conor Masterson.

"I have a soft spot too for centre backs, I liked both of them," said McCarthy after watching them in recent weeks. "They’re both competitive, they can play, they both could pass the ball."

Both Masterson and O’Shea are unlikely to be thrown in at the deep end against Georgia or Switzerland but given the paucity of options that McCarthy now has in defence, they could both get a call-up to the senior squad and may find themselves on the bench.

The Irish manager will just be praying that there are no further injuries that could force them into action.