The defenders will be the only recognised centre-backs in the club's Champions League final later in May due to the suspensions of Branislav Ivanovic and John Terry.
Interim manager Roberto Di Matteo revealed that the pair are still not in group training but is hopeful they will not be sidelined much longer.
"Now we're trying our hardest working towards next Saturday in the hope they'll be in the group training next week," Di Matteo told reporters.
The Blues host Steve Kean’s already-relegated side at Stamford Bridge on Sunday with sixth place their guaranteed final position and Di Matteo revealed his coaches tried to get Luiz ready in time for the game but failed.
"We tried, but he wasn't ready so now we're trying for the last game," the Italian admitted.
"It's difficult to give it as a percentage [chance of appearing in the Champions League final].
"They're at similar stages - not available for Sunday, and next week we'll push them to be available for the group."
Despite not revealing any time frame for when the duo might return, the Italian hinted that their recovery should be soon as they have not been out of action for long.
Di Matteo added: "They've been out three or four weeks, not like three or four months. We have to push them as hard as we can.
Cahill is a major contender for England’s Euro 2012 squad if fit but Di Matteo stressed that he would not feature at the Uefa tournament if he does not fully recover before the end of May.
"We need to think about ourselves and what the club's interests are," he said.
"If he's fine, he'll be available. If he's not, he won't be. As simple as that."