Radoslaw Majewski will miss Nottingham Forest's home game against Middlesbrough.
Majewski was forced off after just 15 minutes of the 4-1 defeat to Millwall at the City Ground on Saturday, with scans revealing the Polish midfielder has damaged ligaments.
Reds boss Sean O'Driscoll is not yet sure how long the 25-year-old will be out.
Jermaine Jenas, who last week extended his loan stay until the new year, was absent against the Lions due to a knock but the Tottenham midfielder has resumed training and could return to the squad.
Greg Halford is available again after serving a one-match suspension but fellow defenders Daniel Ayala (hamstring) and Sam Hutchinson (knee) remain out.
Ayala, on loan from Norwich, is back in training but Chelsea loanee Hutchinson will be sidelined for another four to six weeks having already been unavailable for over a month.
Middlesbrough manager Tony Mowbray has injury concerns - one of which is himself.
Mowbray was forced to pull out of his pre-match press conference due to illness but he is hoping to recover in time to make it into the City Ground dugout.
Coach Mark Procter, who filled in for Mowbray, told the club's official website: ``Tony rang in on Sunday and said he wasn't feeling too well and wouldn't be coming in for training.
``He came in on Monday and was sent straight home by the doc. But he'll be ready for the game.''
Procter is hopeful that Seb Hines will also be fit for the match while Jonathan Woodgate should retain his starting place after coming through the 4-1 win against Charlton on Saturday unscathed.
However, striker Marvin Emnes remains unavailable with a hamstring problem.