Shakhtar Donetsk are set to be without Brazilians Douglas Costa, Fred and Alex Teixiera after six of the club's players refused to return to Ukraine while violence there continues.
The Ukrainian club's owner Rinat Akhmetov confirmed Costa, Fred, Teixiera as well as compatriots Dentinho and Ismaily and Argentine striker Facundo Ferreyra remained in France following a friendly against Lyon.
But president Akhmetov has warned former Manchester United target Costa and the other absentees that they could face sanctions if they do not return to Ukraine.
"Players have contracts that they have to abide by. If they do not come, I think, they will be the first to suffer," Akhmetov told the club's website.
"Hopefully, the mind and heart will prevail over misunderstanding, and the players will not follow temptation and fear. Especially since there is nothing to fear."
Donetsk is at the centre of a violent struggle between the Ukrainian military and pro-Russian rebels and has already forced the Ukrainian Premier League champions to cancel all their matches at the Donbass Arena until the conflict ends.
The Ukrainian season is scheduled to begin this weekend but the Ukrainian Football Federation has yet to decide where Shakhtar will play.
Meanwhile, Newcastle United manager Alan Pardew has dedicated the forthcoming season to two fans who died in the Malaysian Airlines tragedy in Ukraine.
Magpies fans John Alder and Liam Sweeney died when flight MH17 crashed in eastern Ukraine last week, killing 298 people.
They were travelling from Amsterdam to Kuala Lumpur before flying to New Zealand to watch Newcaslte on their pre-season tour.
Pardew hopes the St James' Park club can perform well next season and give grieving families something to remember them by.
"None of us would be sitting here without the fans," he said.
"Owners and managers come and go, as do players, but the fans are always there, and these two guys in particular, to go to the lengths that they did to get out here, has brought home just how important supporters are to us.
"Sometimes when you lose lives in that manner, it puts into context what we do."
Fans of arch rivals Sunderland have put their historical differences with Newcastle aside and raised £22,000 in memory of Alder and Sweeney.