Aaron Hughes has lost his battle to be fit for Northern Ireland's World Cup qualifier against Bulgaria.
Hughes has been struggling with a calf injury since Monday and he broke down just five minutes into a fitness test.
Northern Irish manager Sammy McIlroy had feared as much and he has drafted in Ian Nolan to replace the Newcastle defender at left-back.
McIlroy said: "Aaron Hughes is out. I had never fancied the way it was going to go because he had not been able to do any severe work during the sessions.
"He went out this morning and after just five minutes it was clear he couldn't do it.
"So he drops out and Ian Nolan will come in. There's no problem with Ian and he's an experienced enough player. He will know what's going on."
The Northern Irish chose not to train today and instead went for a walk around Sofia.
Hughes is expected to be the only change from the side which performed so well in Saturday's 1-0 defeat against the Czech Republic.