A broken toe has kept Ryan Tunnicliffe out for the last two games, and he is a doubt to face his former club Fulham on Tuesday.
Millwall boss Neil Harris revealed midfielder Tunnicliffe had played through the pain with the injury, until it became "unbearable".
With Ryan Leonard cup-tied for the EFL Cup third-round clash with the Cottagers, midfield resources could be stretched.
Harris also gave an update on the injured Shaun Hutchinson, who won't be available until after the next international break.
If Tunnicliffe isn't fit to face Fulham, then Jem Karacan will likely start in midfield.
"Tunni has got a broken toe. He had a broken toe and played for a period and he was just getting to a stage where he couldn't really train," Harris explained. "We were putting him into games and then when we brought Ryan in it was an opportunity to say to Tunni 'there's your time to rest'.
"We're hoping we might have him back – pain allowing it – this week, but we can only be dictated to by Tunni's pain thresholds. Last week was just every time he planted his foot and pushed off it was unbearable.
"We're hoping as [broken] toes heal really quickly that he will be back on the training pitch this week.
"Hutch is still going to be a few weeks. We're still looking at the schedule and don't expect him to be, well he won't be back before the international break."
Image: Millwall FC