Gareth McAuley, Chris Brunt and Michael O'Connor have pulled out of the Northern Ireland squad for Friday's friendly against Turkey.
West Brom duo McAuley and Brunt have been key figures for manager Michael O'Neill but will not feature in Adana.
Both men played the full 90 minutes of Albion's dramatic 2-2 draw with Chelsea on Saturday, but Brunt has withdrawn with groin and knee problems and McAulely misses out for unspecified personal reasons.
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, with Hull City defender Alex Bruce a possible replacement for McAuley.
O'Neill would be loath to draw on the country's U21 squad for reinforcements given that they have a European Championship qualifier in Italy on Thursday night.