The Dutchman was withdrawn at half-time during Saturday's 4-0 Bundesliga defeat to Wolfsburg after a collision with opposition goalkeeper Diego Benaglio.

And he has now been forced out of Wednesday's crucial home game with PAOK as a result, though the length of his lay-off has yet to be confirmed.

Schalke go into their clash with PAOK having posted a draw and a loss in their two opening matches of the German top-flight season.

Their form will need to improve if they are to eliminate the Greek club and take a place in the Champions League group stages for the second consecutive year.

Doing so without Huntelaar will be a big ask, however, with the 30-year-old having proved a vital source of goals for Schalke since his arrival in August 2010.

Huntelaar has netted 80 goals in 119 appearances for Jens Keller's men, including 21 in 27 European outings.