Adam El-Abd will miss the next month of Brighton & Hove Albion's push for a play-off spot.
The 23-year-old, who can play in defence or midfield, suffered a knee injury during Tuesday's 2-1 defeat at Huddersfield Town.
El-Abd damaged medial ligaments at the Galpharm Stadium and is expected to be sidelined for at least four weeks.
Brighton boss Dean Wilkins will now try to bring in short-term cover on loan after ruing the injury to El-Abd.
"To lose Adam at this stage of the season is a major blow, particularly as he has been in exceptional form," Wilkins told the club's official website.
"We will now do everything we can to bring someone in."