Millwall are hopeful Andy Keogh will be fit for the south London derby at Crystal Palace on Saturday.
The striker was ruled out of the Republic of Ireland's qualifier against the Faroe Islands after suffering mild concussion in training over the weekend.
But Lions manager Kenny Jackett told the club website: "Andy has been for an X-ray, and our medical staff believe there is cause for optimism.
"While the radiologist will have the final say, we are hopeful that things will settle down over the next couple of days and we can then assess the situation later in the week.
"At this stage the news is by no means conclusive but the signs do appear to be positive."
The 26-year-old has scored twice for the Lions so far this term and also netted the Republic's consolation goal in their 6-1 thrashing at the hands of Germany on Friday.