Kyle Lafferty is to undergo a scan on the knee injury which forced him out of Northern Ireland's 1-1 draw with Poland on Saturday.
The Rangers striker had looked bright during the 2010 World Cup qualifier, and forced a 37th minute breakthrough to hand the Irish the lead.
However, he hobbled off shortly after the interval to be replaced by Burnley's Martin Paterson.
Lafferty is now facing a race against time to be fit for a crunch midweek showdown with Slovakia.
"The situation with Kyle is ongoing, but we will know more after the scan," said Northern Ireland boss Nigel Worthington.
Lafferty's team-mates know how important his physical presence could be on Wednesday and Motherwell defender Stephen Craigan is hoping the burly frontman pulls through.
"Kyle was having a great game and asking questions of Poland," he said.
"He was winning things in the air and getting in behind them.
"That was his best 45 minutes in a Northern Ireland jersey, but then unfortunately he had to come off."