Owls captain Anthony Gardner could miss more than half the season if the club’s worst fears are confirmed.
He was carried off at Middlesbrough on Saturday having shown the classic signs of a ruptured Achilles tendon.
This type of injury rules a sportsman out for a long period. Well-known footballers who suffered it include David Beckham and John Barnes and they were both sidelined for five months.
Owls boss Dave Jones picked up a less serious Achilles injury in his playing career and even that kept him out for more than two months.
A tear is caused by the tendon coming under sudden strain but to the player it can feel as if he has been kicked in the back of the leg - which is the symptom that Gardner experienced.
Jones said: “We fear the worst. We’ve just got to get him back as quickly as possible.”
It leaves the club down to three main centre halves, with Jones having already been in the market for a midfield player, a striker and a goalkeeper and having signed right back Jordan Spence on an emergency loan from West Ham because of Lewis Buxton’s hamstring problem.
Miguel Llera is Gardner’s immediate replacement, and Spence can also play centre half. Jones said he did not expect to be able to sign more new players before today’s deadline: “Not unless we can shift one or two and it enables us bring one or two in.
“It’s no use moaning. We’re getting on with it and we’re digging deep.”
Spence, who made his debut on Saturday, is due to be with the club for a month: “Then we’ll send him back, unless Sam (Allardyce) helps me out again,” said Jones.
The Owls boss shrugged off the injury setbacks: “It gives others an opportunity to stake their claim and keep the shirt. When we play like that (in Saturday’s 1-1 draw), we’re not far away.”
Striker Caolan Lavery was due to be on the bench but felt a calf niggle so was replaced by Llera.