Sheffield United defender Jack O'Connell could miss the rest of the season with a knee injury, according to manager Chris Wilder.
O'Connell, 26, was tipped for an England call-up last season after impressing for the Blades, who finished ninth on their top-flight return.
That was largely because of a solid defence, which kept 13 clean sheets.
"Jack O'Connell is possibly out for the season and needs a knee operation," Wilder said.
"He tried to come back and then had to have a scan. It is a huge blow for him and us.
"He adjusted pretty quickly and established himself in the Premier League last season."