Andy Keogh has given Millwall an injury scare ahead of Saturday's south London derby at Crystal Palace.
The striker was ruled out of the Republic of Ireland's World Cup qualifier against the Faroe Islands on Tuesday after suffering mild concussion in training over the weekend.
An FAI spokesman said: "Andy Keogh suffered a knock to the head in training on Saturday. He was observed overnight by the FAI medical team and has been ruled unfit to travel to the Faroe Islands due to mild concussion."
Keogh, 26, has scored twice for the Lions so far this season and set up Darius Henderson's late winner against Bolton last weekend after coming off the bench.
He also scored the Republic's consolation goal in their 6-1 drubbing by Germany on Friday.