The nature of VfB Stuttgart and Guinea forward Serhou Guirassy’s thigh muscle injury is to be determined via an MRI scan, Stuttgart sporting director Fabian Wohlgemoth said on Tuesday. Guirassy sustained the injury in Monday’s 2-0 win over Nigeria in an Africa Cup of Nations tune-up match in Abu Dhabi. The almost month-long continental tournament in Ivory Coast starts on Saturday, and Guinea’s first game is on Monday against Cameroon. Wohlgemuth refused to speculate on the injury before scan results have arrived, saying that “remote diagnoses are not useful” but that they are in contact with G…