Ireland striker Callum Robinson will miss at least three months with a hamstring injury.
The Preston North End star was forced off after scoring in their 4-1 win over Blackburn on Saturday.
It will be decided this week if the 23-year-old needs surgery.
PNE manager Alex Neil said: "Callum is going to be out for a minimum of three months, and we will get an opinion on that this week as to whether he will need surgery.
"It’s really bad news for everyone connected with the club, because he has been our talisman this year.
"It's the first real injury of his career and naturally he's gutted, and we are all gutted for him.
"He is having the season of his life and so it's hugely disappointing for everyone at the club. The other lads will be disappointed too, they are all good mates."
Robinson played in both of Ireland's games, scoreless draws against Northern Ireland and Denmark, during the international break.
Speaking after Saturday's game, Neil blamed that workload for the injury.
"The international break has caused us a real issue. Callum has done so much over the break when the rest of the team are resting and that causes an issue," he said.
His strike partner at club and country Sean Maguire has also been ruled out until January with a hamstring injury, sustained in the Northern Ireland match.
Ireland's qualifiers for Euro 2020 will begin in late March.