Gareth McAuley, Chris Brunt and Michael O'Connor have withdrawn from the Northern Ireland squad for the friendly against Turkey on Friday.
West Brom duo McAuley and Brunt have been key figures for manager Michael O'Neill and their loss - Brunt to groin and knee problems and McAuley for unspecified personal reasons - will severely weaken the squad. Both men played the full 90 minutes in Albion's dramatic 2-2 draw with Chelsea on Saturday.
The further absence of nine-cap Rotherham midfielder O'Connor, who has a thigh injury, leaves O'Neill with just 18 players at his disposal.
No replacements have been announced at this stage, but such a paucity of numbers makes it probable that the likes of Barnsley winger Paddy McCourt could be called up to cover for Brunt, while Hull's Alex Bruce would be a possible replacement for defender McAuley.
O'Neill would be loathe to draw on his the country's under-21 squad for reinforcements given that they have a European Championship qualifier in Italy on Thursday night, just a day before the senior game in Adana.