New Schalke signing Coke has suffered a cruciate knee ligament injury on his debut for the club and is facing a potentially lengthy spell on the sidelines.
The Bundesliga club sealed the 29-year-old's signing from Sevilla last Sunday, but received a massive blow in the defender's first match.
Coke played in the first half Schalke's 2-1 friendly victory over Bologna in Austria on Thursday, but picked up the injury from what the club described as a "heavy challenge" and is now set for a long-term absence.
Schalke's statement read: "The Spaniard damaged the cruciate ligament in his right knee and will consequently be out of action for the foreseeable future.
"The 29-year-old featured for 45 minutes in the game and developed pain in his right knee after a heavy challenge. Tests have established that ligament damage has been sustained, with the severity to be determined over the course of the next few days."
Schalke chief executive Christian Heidel was despondent after the blow.
He said: "We are shocked. Our thoughts are with Coke at this point, least of all because he had already settled in well here.
"We will support him however possible throughout the lay-off."
Coke had initially seemed unaware about the extent of his injury, posting an image on Twitter him in action during his debut.