Jefferies revealed Skacel, who has scored seven goals in 12 appearances since he re-joined the Gorgie club in the middle of September, had been nursing a calf tear in recent weeks and the injury had started to cause the Czech Republic internationalist a bit more aggravation.
He would have missed the Boxing Day trip to Kilmarnock had it not been postponed due to the bad weather and will now almost certainly sit out tonight's SPL clash in Paisley instead.
But Jefferies said the decision was being taken more as a measure to prevent the injury becoming a longer-term problem and is hopeful Skacel will be back in his plans for Saturday's showdown with Hibs at Tynecastle.
"Rudi has a bit of a calf tear. He's had it for a few weeks but has managed to get through games," said the Hearts manager.
"He felt it was starting to aggravate him a wee bit more and the physio feels that if missed a game at moment it might mean him not being out for so long if the injury gets worse. If he played it might have put him out for five or six weeks, which I think everyone was assuming was the case. But we think he could be okay for the weekend if he misses out against St Mirren."
Admitting he had a doubt over one other player who would also have missed the trip to Rugby Park, Jefferies said he didn't feel he needed to take any risks for tonight's match.
"I have been going on recently about the fact we have a strong squad and there are people bursting for their chance," he added.
Meanwhile, the Hearts boss is not ruling out any new signings in the January transfer window but admits it would take someone "exceptional" to add to his squad at a time when Lee Wallace is set to make a return, Andrew Driver isn't far away and Suso Santana shouldn't be too far behind him.
"Sergei (Fedotovas) and I have been in touch by phone a couple of times because we are still waiting for a chance to sit down and speak about things," he said.
"We will hopefully do that early in the new year but I think it is just a case of catching up and getting some thoughts on players who are maybe not playing at the moment, even those who are playing.
"Everybody is thinking that, with the transfer window about to open, we are probably going to be going out and adding a couple of players.
"That would be nice as the stronger the squad the better. But the squad is doing so well that it would take something exceptional to come in and enhance us at the moment.
"Right now that is going to be difficult to do. It would take a huge signing because we have even a strong bench.
"It is always good for players and supporters when a new face comes in. If there is a chance we will look at it, if not we'll go with what we've got.
"Then we'll assess that again at the end of the season."