CLUB captain Paul Robinson could miss the rest of the season after suffering a fresh injury setback during his rehabilitation.
Robinson, who only resumed light training a fortnight ago, is expected to have surgery on what is being described as a "complex groin problem."
The 31-year-old went under the knife last summer to correct a double hernia but since then he has been kept in the treatment room by a string of complications.
Millwall said in a statement: "Robinson is set to fly out to Philadelphia for a review of the problem. He will see a prominent surgeon whose speciality is complex groin cases."
Earlier this season, Robinson admitted the Lions' rise up the Championship table had been a major comfort to him during his recovery.