The Rugby Park side have been hit with a catalogue of injuries in recent weeks and in their last outing, a 2-1 home defeat to St Mirren, Jefferies' squad was stretched to the limit.
The Killie boss was forced to name young keeper Lee Robinson as a substitute outfield player, while Iain Flannigan sat on the bench even though he was struggling with gastro-enteritis.
Jefferies is counting on Jamie Hamill and Danny Invincibile recovering from their respective knee and hamstring injuries to bolster his squad and give them a fighting chance - and a full complement of players - ahead of the trip to Tynecastle.
"In our last game against St Mirren, we had Lee Robinson, who is is our third goalkeeper, stripped as an outfield player to make up the numbers," the Killie boss told Press Association Sport.
"Iain Flannigan had gastro-enteritis but he was on the bench.
"He really shouldn't have been there but we had to make up the numbers.
"With 10 minutes to go, when I wanted to change the game, the only option I had was Graeme Owens and he is only a young player who we are hoping to step up in the future.
"The rest were defenders - or keepers.
"But if we get Hamill and Invincibile back it will look better and of course, keeper Mark Brown has come on loan from Celtic and he looks as if he has a real spring in his step because he has the chance to play first-team football."
Brown was recruited as cover for Alan Combe who is in hospital for a hip operation and Jefferies is still without some of his other top players, with striker Mark Burchill facing surgery to mend an Achilles problem and midfielder Jamie Fowler recovering from a hernia operation.
However, there was some good news for the former Hearts boss as striker Kevin Kyle could be back for the match against Rangers next week.
Kyle had to withdraw from the Scotland squad for the recent World Cup qualifiers against Macedonia and Holland to have an operation to repair a torn cartilage in his knee.
Jefferies said: "The Hearts game has probably come too early for Kevin but it looks like he will be fit for the following week."
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