Paddy McNair, Conor Bradley and Bailey Peacock-Farrell have been ruled out of Northern Ireland's friendly against Luxembourg on Friday.
McNair will not make the trip this week after suffering a foot injury in Middlesbrough's FA Cup quarter-final defeat to Chelsea on Saturday.
The versatile 26-year-old joined up with Ian Baraclough's squad in Belfast but will remain behind to continue treatment, with a chance he returns for next Tuesday's home match against Hungary.
Liverpool right-back Bradley is yet to join up with the squad having remained on Merseyside for assessment on a knee problem.
Similarly, goalkeeper Peacock-Farrell, who is at Sheffield Wednesday on loan from Burnley, is yet to join up with the squad and will miss the Luxembourg trip, although the 25-year-old should come into contention for the Hungary match.
It is understood that Peacock-Farrell is not injured and will be available for the Owls' League One match against Cheltenham on Saturday before joining Baraclough's squad. Conor Hazard and Luke Southwood are the other goalkeepers available for Northern Ireland.
Baraclough's options were boosted on Monday with news that Leicester defender Jonny Evans will be available for the Luxembourg trip, having not been named in the original 25-man squad.
Evans (34) has been battling a long-term foot injury but after managing 25 minutes of Leicester's 2-1 Premier League win over Brentford on Sunday, he will make the trip to Luxembourg.
However, Evans will not be available for the Hungary match as he manages his return to action.