Barry Bannan and Keiren Westwood have both suffered setbacks during their recoveries from injury, Sheffield Wednesday manager Jos Luhukay has revealed.
Midfielder Bannan and goalkeeper Westwood had been expected to make returns to the Owls squad in the next few weeks after recommencing training with the first team following hip and groin injuries respectively.
But both will now be delayed after encountering further problems during training.
"Barry Bannan has this week not be training with the team," Luhukay said.
"He trained with the team two times but he had another injury come.
"So in the last days he has only been with the medical officials.
"For the next games I think he is not an option.
"Keiren last week trained two or three times but he also now has a problem with the injury.
"I cannot now say when he will be coming back to 100 per cent."
On a timescale for Bannan's return, Luhukay said: "It is difficult to say.
"He had a good preparation and a good situation with the physios to be training very well but he trained one time with the team and had a little bit of problems.
"We must now give him the time to come to 100 per cent back for team training and see how it is going."
There was more positive news on the injury front for defensive duo Tom Lees and Joost van Aken, who should both be back in full training next week after recovering from respective groin and hamstring injuries.
But on long term injuries to the likes of Gary Hooper, Sam Hutchinson and Steven Fletcher, Luhukay says Wednesday will still be without them for some time.
He said: "We have a long list.
"We had the hope that Barry Bannan could come back but we now have one week where it is not a good situation for him.
"Tom Lees we hope that maybe today and next week he will be starting training with the team 100 per cent.
"He has trained one time with us so we must have a lot of patience so that they will be an option for a game soon.
"Joost van Aken will come next week back to the team training.
"All the other players are a couple of weeks further from coming back to the team training."
One player who may be available for Saturday's clash with Birmingham City at Hillsborough is Marco Matias, who sat out Tuesday's draw at Middlesbrough through injury.
The Portuguese forward will training with the senior team on Friday.
Luhukay said: "Marco had, the day before the game with Middlesbrough, problems with his leg so he could not train the last training before Middlesborugh.
"It was a high risk to let him play so the medical team and the staff decided he was not with the squad.
"We have the situation where he will train today [Friday] and we hope that he can train 100 per cent so that maybe there will be a position for him tomorrow in the game against Birmingham."