Striker Will Grigg is set to miss Northern Ireland's World Cup qualifiers against Russia and Israel.
The in-form Walsall player made his first international start in last month's goalless draw in Malta and was favourite to lead the line against Russia in the absence of the suspended Kyle Lafferty.
But he was unable to train on Wednesday due to a hamstring problem and it is understood he will play no part in the Belfast double header.
Manager Michael O'Neill, still chasing his first win at the helm, has a number of options up front but none with a proven record at this level.
Burnley's Martin Paterson, back in the fold after a self-imposed exile, will be expected to start as a lone striker but O'Neill also has Inverness forward Billy McKay and Aberdeen pair Niall McGinn and Josh Magennis available.