Northern Ireland's most capped outfield player Aaron Hughes is a doubt for the double header with Germany and Norway next week having coming off injured on Saturday.
Hughes, who turns 38 next month, was substituted after just seven minutes playing for Hearts at Dundee with a calf issue that he was struggling with prior to the game.
It could rule him out of Northern Ireland's clash with world champions Germany in Belfast on Thursday and the trip to Norway three days later as Michael O'Neill's side look to book one of the eight World Cup qualification play-off places available.
"We knew he might struggle with his calf injury," Hearts boss Craig Levein said of Hughes. "We decided to give him a chance but obviously it didn't last and forced us into the change."
Even at 37, Hughes would have been expected to make his 109th international appearance against the Germans.
His next Northern Ireland outing will take him beyond England's Bobby Moore as the home nations' most capped defender of all time.
Hughes, who earned his first ever international senior call-up 20 years ago this month, had initially retired from Northern Ireland duty in 2011 before performing a U-turn when O'Neill took over.
"It's a fantastic achievement for him if he surpasses someone like Bobby Moore," O'Neill said earlier this week.
"Whilst Aaron Hughes won't be spoken about in the same breath as Bobby Moore, I think his achievements as a player are an example to others, very much like Gareth McAuley, because he's got the maximum possible out of his career.
"When you look back on your career, that's the best you can ask for, that you did everything possible and got the most out of it. Aaron Hughes has certainly done that."