The Easter Road boss has made no secret of his desire to bring in another attacking option after Aiden McGeady was ruled out for up to 12 weeks after suffering a recurrence of a medial ligament issue.
“Whether it is Martin or anyone else, I do feel we need one more, a different style,” Johnson said.
"Elias Melkersen is doing a good job in that position at the moment but naturally he’s a nine. We potentially have room to bring one more in. If that’s Martin, great; if not, we go back to the drawing board.
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“It won’t be cheap, it would take a big investment from the ownership.”
Asked if Boyle was keen to strike a deal to return to the Capital club, Johnson answered in the affirmative.
"It’s my understanding [that Boyle is keen to come back] but I’m talking out of turn effectively, because he’s not our player.
"I’d be disappointed if somebody else was talking about one of our contracted players in those terms.”
Johnson is only too aware that the complex nature of the transaction may see negotiations drawn out until the end of the transfer window – or perhaps even beyond.
“It’s a fine balance. We’re prepared to play the waiting game but don’t want to lose the opportunity to get someone else who’s good,” he continued.
"If Lionel Messi becomes available – see you Boyler, we’re taking him! That’s the ruthless nature of football but while there is communication, it means there’s a chance, and while there’s a chance, we’ll wait.”