Gelsenkirchen - FC Schalke 04 striker Klaas-Jan Huntelaar has suffered a setback in his bid for full fitness.
The Dutch international returned to team training on Monday following a two-month injury lay-off, but his involvement did not last long following a collision with a team-mate.
Huntelaar suffered bruising to the same right knee which has kept him out of action since the Matchday 2 defeat to VfL Wolfsburg and now faces an anxious wait to find out the severity of the injury.
The Royal Blues travel to Eintracht Braunschweig on Matchday 9, before facing Chelsea FC in the UEFA Champions League and Ruhr rivals Borussia Dortmund in the space of just four days.
Find out what the Revierderby is all about on the official Bundesliga YouTube channel: