Middlesbrough defender Daniel Ayala will miss the next four weeks after sustaining an ankle injury.
The 24-year-old joined Boro for £350k from Norwich City last month, after a loan spell in which he scored three times in 13 Championship appearances.
Ayala has started the club's last nine league matches, during which time they have kept seven clean sheets.
His absence, along with that of Rhys Williams, could see loanee Kenneth Omeruo deputise at centre-half.
The Nigerian made his debut at right-back in Saturday's goalless draw with Doncaster Rovers.