Motherwell manager Mark McGhee says the club are "very concerned" about midfielder Carl McHugh's head injury.
McHugh, 23, has not played since a collision with Kilmarnock's Dean Hawkshaw on 6 August that left him with delayed concussion.
"It is really grim," said McGhee. "He is having a really difficult time and we are very concerned about that.
"It has not made much progress. It is just not getting better. We are doing everything we can."
Republic of Ireland Under-21 cap McHugh, who has over 160 senior club appearances, joined Well in the summer from Plymouth Argyle and the win over Killie at Rugby Park was his third appearance for the Steelmen.
"There is no time given to this injury," McGhee added.
"They don't say it 'will take six weeks or eight weeks', they actually say 'it could take six weeks, eight weeks, it could take six months'. That is the nature of it and we just hope it doesn't take six months obviously.
"It is a complicated and nasty condition that he has ended up with.
"He is seeing a guy in Dublin actually this week to put his mind at rest."
Meanwhile, McGhee confirmed defender Joe Chalmers is to have a groin operation next week and will be out for six weeks, but midfielder Chris Cadden has recovered from a hamstring injury and could return against Celtic in Glasgow on Saturday.