Reds head coach Markus Schopp has revealed that Morris, who has made a big impact since joining the club from Norwich City in January, will be out for ‘six to eight weeks’ after injuring his knee in Saturday’s victory over Coventry City at Oakwell.
Morris came off in the first period and was wearing a knee brace in the West Stand during the second half - with scans having now revealed the extent of his injury.
Meanwhile, it is understood that work permit issues are a reason why Belgian duo Oulare and Leya Iseka have yet to feature for Barnsley, allied to the fact that pair are also lacking match sharpness.
Big frontman Oulare, 25, who turned down a move to Oakwell in January, joined the club at the second time of asking last month from Standard Liege - and is viewed as a like-for-like replacement for loan forward Daryl Dike, who returned to parent club Orlando City at the end of last season.
Former Belgian under-21 international Leya Iseka, 23, joined the club from Toulouse in early August.
On Morris, Schopp, whose side visit QPR this weekend, said: “The information I have is that Carlton will be out for six to eight weeks. It is something that is a tough one for us.
“He is a guy who gives us a lot.
“It is a knee injury and we were fortunate because it could have even been worse and we have to take it and prepare him and bring him back as soon as possible.
“But we were actually lucky as it could have been worse.”
Confirming that Oulare and Leya Iseka will again be unavailable, with their debuts on hold, Schopp added: “They will not be available for the next game and we have to take care of our guys as we have done in the past couple of weeks and I am convinced we can do this.
“It is my aim to have them at least for when the international break is over. But we are looking forward to having them back as soon as possible.
“Of course, it is a tough one for everybody because everybody wants to play and contribute and take responsibility for development. It is important we all know how to handle it and it is tough for each player to get through something like that.
“But at the end, we will have two players who are prepared and who will give us what to expect from them.”