Millwall defender Mark Beevers has been ruled out for six to eight weeks with a knee injury.
The centre-half suffered sprained medial ligaments during Saturday's 1-0 win at Charlton - Millwall's first clean sheet of the season.
Lions boss Steve Lomas told the club website: "It's obviously a blow for us and for Mark at a time when we appear to be turning a corner.
"Fortunately surgery doesn't appear to be necessary but we are resigned to being without him for the next few weeks."
Karleigh Osborne or Danny Shittu could replace Beevers against Leeds at The Den on Saturday.