The centre-half has been out since November with a knee injury and has been told the troublesome joint will not clear up in time for him to feature again this season.
But McCombe still has just under 18 months left on his contract and Johnson insists he is a part of his future plans.
"Every now and again a situation occurs where someone is really unlucky and that is the case with Jamie. He's signed a contract and then been ruled out by long-term injury," he told the Evening Post.
"But we are looking after him, he has time on his side and I'm sure we will see him back playing in the future."
Source: PA
Source: PA