Middlesbrough captain Emanuel Pogatetz has suffered a setback in his bid to return to full fitness.
The Austrian defender has been sidelined since the end of last season after knee surgery.
He made his comeback for Boro reserves last month and had hoped to be on the verge of a first-team return.
But Boro boss Gareth Southgate has confirmed that Pogatetz has suffered a setback.
"Pogatetz has had a setback training-wise so we need to have a close look at him this week," said Southgate.
"He is an experienced player and we need him back in the squad as soon as possible.
"But we have to be careful in how we deal with him, because when he comes back we need to know that he is definitely ready."