Some reporters suggested the shortage of substitutes in the tie was flashing a message to owner Ellis Short in the January transfer window that reinforcements were needed just to field a full squad.
West Ham boss Sam Allardyce admitted he did the same thing two weeks ago, but O'Neill insists the owner "knows full well we need players, I don't have to make the point".
Martin O’Neill: “It wasn’t a prank, it’s just the way things are.
“We don’t have the biggest squad, and we’re really stretched at the moment.”
"Stephane Sessegnon was due to be the seventh substitute, but he had to cry off before we boarded the plane, and we decided against just giving the shirt to some young player for the sake of it.
“We maybe could have called one of the younger players in, but there’s a danger that some young lad gets a shirt and then all of a sudden he thinks he’s part of the team.
“I don’t want that. I want the young players to earn that shirt, I really do.
“But don’t think that this was some sort of well-thought out masterplan – it was very late in the day when Sessegnon found he was too sore to come, and it became a bit of a problem.
“The fact is that we are short on bodies and we are going to do something about if we can – well, not if we can, we NEED to do something about it.
“I’ve had conversations with the owner and think I get on reasonably well with him.
“He’s well aware that we need to strengthen, and he wants to do something about it.”