The 21-year-old will have surgery Tuesday after tearing a knee ligament in the weekend defeat to Hannover.Schalke left back Sead Kolasinac could be out for at least six months after suffering an anterior cruciate ligament tear in his right knee.
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The Bosnia-Herzegovina international was forced from the field 16 minutes into Saturday's 2-1 defeat at the hands of Hannover in Schalke's opening Bundesliga match of the season.
Subsequent tests revealed a tear, and Kolasinac is expected to undergo surgery Tuesday, according to a statement released by the club via its official website.
The 21-year-old, who featured twice for his country at the World Cup in Brazil, made 24 league appearances for Schalke last season.
Kolasinac was quoted during the close-season as saying he had been offered a move to the Premier League with Manchester United.
However, a transfer failed to materialize, with Louis van Gaal ultimately moving to sign Argentina international Marcos Rojo in a 20 million euro deal from Sporting.
Schalke takes on reigning Bundesliga champion Bayern Munich next Saturday in its second game of the new season as it looks to bounce back from a disastrous start to 2014-15.
Jens Keller's side was stunned by Dynamo Dresden in the DFB-Pokal, 2-1, before Saturday's defeat by the same scoreline to Hannover, but general manager Horst Heldt insists it is too early to panic.
"If you lose twice in a row, then it is something you can unfortunately not avoid," he said. "We must stand [together] as Schalke. But what is important is what is being discussed internally with us. We do not discuss the coach.
"The good thing about football is that a season is not already decided after the first matchday."