It was reported that the SPFL have launched an investigation into the matter, and should the club be found to have breached the rules they could receive anything from a heavy fine to a points penalty.
The signature, it was alleged by a former member of staff at Rugby Park, was forged so that an unknown player could be registered in time for Kilmarnock's match against Celtic on March 14. However, all of the players who were included in the squad against Celtic had already featured for Kilmarnock earlier in the season, casting doubt on the claims. Johnston said he would be shocked if the allegations turned out to be true. "As far as I'm aware, everyone was registered," said Johnston. "The first I knew about it was this morning when I read the paper. You know as much as I do, so far. I've not spoken to the chairman.
"Honest to God, that's the first . . . I don't even know anything about it. We've just got to make sure there cannot be any distractions. That's what we spoke about with the players this morning. We had just a quick chat to tell them that I didn't know anything about it."
Kilmarnock fans have been living in interesting times. Supporters and the club chairman were at war, Rugby Park has been boycotted, and the playing budget slashed ruthlessly. On the bright side, the first-team squad is, at least, used to dealing with distractions. "There's been a couple," admitted Johnston, with a wry grin. "But that's probably part and parcel of football. We've just got to focus on what will happen at the weekend. There's nothing I can do, there's nothing the players can do."
Ross County lie in wait tomorrow, at the end of the long trip north. Kilmarnock had looked one of the more likely clubs to escape the relegation play-off but are now just two points from guaranteed safety after surrendering a lead to lose last week at home to Partick Thistle.
"I still don't think one win is going to be enough, we're going to have to win a few games," Johnston said, looking ahead to tomorrow's game. "Everybody's dragged in, you can see how tight the league is.
"We face a tough test [at County] I don't think there was much in it last week, we were a wee bit unfortunate not to get anything from the game. But at this stage of the season it is results that count."
In the minds of many, Kilmarnock and St Mirren - of the five clubs involved in the lower-half scrap - are the most likely to drag themselves out of trouble for one reason. They both have a proven, experienced goalscorer. Stephen Thompson's contribution in Paisley has matched that of Kris Boyd's at Rugby Park, as Johnston acknowledged.
"Every side is crying out for a player like him," he admitted, before insisting his players were relaxed about the challenge ahead. "[The training session] was really bubbly, really bright, no nervousness at all. You could see that they were all desperate to play."
There was certainly no sign of nerves at the training complex. Manuel Pascali had grinned in the background as he walked past. "Sold out today!" the Italian shouted at the throng of camera-wielding, eager journalists who had arrived with the sniff of a breaking story.
Tomorrow, football will again take over. Kilmarnock have played five games, losing four, since the club agreed a deal to eradicate their debt and effectively put an end to months of off-field turmoil.
There is just a little swirling around the club again. Perhaps it will make them more comfortable.