Star player Conor Bradley has not featured for club or country since knee surgery in January and O'Neill told BBC Sport NI this month that he always suspected the injury "was going to take longer than maybe some people were thinking" before adding it would be a "bonus" to see him in a green jersey before March 2027.

The 23-year-old has missed six of Northern Ireland's past 14 games through injury, and another thanks to a one-game suspension, but in many ways it has been a case of trying to replace the irreplaceable.

The Liverpool full-back tends to play in a more advanced role for his national side on the right-side of a 3-5-2 and, while O'Neill has other natural options for down the flank, none possess the same mix of attacking drive and defensive instinct.

Nor is Bradley the only injury concern before the squad announcement.

Midfielder Ali McCann injured his hamstring in Preston's 4-0 Carabao Cup defeat by Everton last month with his club manager Paul Heckingbottom saying his captain would be out for "months".

O'Neill has previously spoken about how the 26-year-old is the sort of player whose importance is highlighted in his absence and his injury leaves a hole in the starting XI alongside Fulham's Shea Charles in the preferred double-pivot.

The summer transfer window has again been a busy one for O'Neill's squad with a number of players making moves either on a permanent or loan basis.

Justin Devenny's Stoke career got off to a flying start with a double on his first start since his switch from Crystal Palace. A natural left-footer, he has given NI balance as a wing-back since his debut in June 2025.

A versatile player, Devenny has been turning out as a central midfielder for the Potters and could be one to fill the void left by McCann, as he did in the World Cup play-off defeat by Italy in March.

Oxford United's Brodie Spencer, if he is not needed to replace Bradley on the right, would then be an option to step into the left-wing back role.

Deploying Devenny's new club-mate Ethan Galbraith in a deeper midfield role is another option, one with the added benefit of getting the former Swansea City player on the ball with more frequency.

With Isaac Price sure to fill one of the more advanced midfield positions, using Galbraith elsewhere would then leave O'Neill with a decision to make regarding the slot beside the West Brom man.

Jamie Donley has started as a centre-forward in the side's past five games, scoring against Luxembourg and Wales since first being deployed as a nine, and it feels unlikely he would be moved into a deeper role now.

Patrick Kelly and Callum Marshall are options, but could O'Neill be tempted to throw an exciting but unproven attacking talent in at the deep end?

Liverpool's Kieran Morrison, spending the season on loan at Sheffield Wednesday, Arsenal's Ceadach O'Neill and Braiden Graham of Everton, were all part of the squad in June with the former pair making their international bow in the friendly victory over Guinea.

O'Neill, who drew praise from Mikel Arteta during pre-season, also appeared off the bench against France four days later.

While competitive internationals would be a step up, Michael O'Neill has never been shy to give young players an opportunity before they have established themselves fully at club level.

Nobody connected with Northern Ireland will have fond memories of when the side last faced so congested a fixture list.

As a consequence of the Covid-19 pandemic, the June 2022 window similarly contained four games, with then manager Ian Baraclough presiding over losses to Greece and Kosovo, as well as a pair of draws with Cyprus.

Indeed, if not for an added-time equaliser from Jonny Evans against the Cypriots at Windsor Park, results would have been worse.

There is little doubt that such a schedule places greater demands on countries with fewer playing resources.

While, with everyone fit, there was a sense during the last Nations League campaign that O'Neill had settled upon his favoured starting XI, a trio of friendlies so far this year have given him the chance to assess further options.

In four games in 2026, O'Neill has used 27 players, including 21 in the game against Guinea alone.

Like Bradley, Sunderland's Daniel Ballard has not played for the side in this calendar year through injury, while the likes of Dion Charles, Bailey Peacock-Farrell and Jamal Lewis are among a group last selected in November 2025.

Approaching the four-year anniversary of his return to the job, it will be interesting to see whether O'Neill feels his first four-game window forces him to rely more heavily on the depth he has built across this year.