NI veteran Hughes a doubt for WC Qualifiers
Northern Ireland's most capped outfield player Aaron Hughes is an injury doubt for the double header with Germany and Norway next week.
Hughes, who turns 38 next month, lasted just seven minutes of Hearts's game at Dundee on Saturday before being withdrawn.
He had been struggling with a calf problem prior to the game.
With Northern Ireland playing host to world champions Germany on Thursday and travelling to Norway three days Hughes could be watching from the sidelines.
Hearts boss Craig Levein said, "We knew he might struggle with his calf injury.
"We decided to give him a chance but obviously it didn't last and forced us into the change."
Had he played, Hughes would have made 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.
The Cookstown born defender, 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."