Middlesbrough captain Emanuel Pogatetz faces a knee operation which will rule him out for the rest of the season.
Pogatetz has been out of action since picking up the injury in the 4-1 defeat to Bolton at the start of April.
Boro boss Gareth Southgate was hoping rest might cure the problem, but the Austrian now looks set to go under the knife to rule him out of his side's last three games of the campaign.
"I think Emanuel will be out for the season now and that's been a blow for us," said Southgate.
"He's had a problem with his knee and we've tried to use rest as a form of recovery.
"It's likely that he will need an operation. We've put that off as long as we could, we've tried every other course of action but, unfortunately, it looks as if an operation is required."
Meanwhile, Boro goalkeeper Jason Steele has signed a new three-year deal at the club.