Steve Bruce fears Sheffield Wednesday loan defender Achraf Lazaar could be sidelined for “at least six weeks”.
The left-back, 27, made an impressive debut in the Owls’s 3-1 win over Swansea City on Saturday, before limping off in Tuesday night’s 2-0 win over Brentford.
It was only the Morroccan international’s second game for the Owls - since joining from Newcastle United in January - but he was due to have a scan today on his hamstring injury.
“We are looking at weeks, at least six I would have thought,” said owls boss Bruce, meaning he will definitely miss Monday’s Steel City derby.
“We won’t know the severity of it until this afternoon when he has a scan. We have let him have 48 hours until we can re-assess it.
“Once he has had the scan we will know a little bit more.
I have to say, the early stages don’t look good. Fingers crossed it’s not as bad as we fear.
“The intensity of the Championship is huge. I should have been a bit better with the boy. With Fox injured, and the lad was beaming - he had a great debut - but I am kicking myself.
“I have been in the game a long, long time, and it’s common sense.
“He hadn’t played in a long time, then to play him twice, the intensity of the games is huge. Lazaar did 11.5km on Saturday, and you are asking him to go back into the race do it again. Maybe he wasn’t ready.”
The Owls also have injury doubts over Morgan Fox, Lucas Joao and Jordan Thorniley ahead of Monday’s game.
Long-term, Bruce plans to investigate why Wednesday have struggled with a long injury list for the last two seasons.
At one stage last season, the Owls had 16 first-teamers ruled out with injuries.
He said: “We had 10 injuries now with Lazaar, that’s ridiculous numbers.
“It’s something which I have to address.
“I don’t know a club like it - with long-term injuries. You get one, but we have had four or five, which is not very good.
“The most important thing for me is getting the team to perform in a certain way, and get a result.
“But looking long-term, in the next few weeks and months, we have to ask why? It could be we have just been unlucky.
“But, certainly, when you see the amount of long-term injuries the club has had, over the last 18 months, it’s not good.”