Arsenal face a defensive crisis ahead of Saturday’s FA Cup final against Chelsea with Gabriel ruled out with a knee injury and Laurent Koscielny suspended after being red-carded against Everton last weekend.With Shkodran Mustafi also an injury doubt, manager Arsene Wenger is running out of central defensive options.The only good news was that Brazil defender Gabriel’s injury is not as bad as first feared when he was taken off on a stretcher in Sunday’s league finale.”Gabriel is out for six to eight weeks,” Wenger told a news conference on Wednesday. “We had a scare about his cruciate but it’s medial. He avoids surgery.”Shkodran Mustafi, we have some worries, because he is still sick at the moment. He has not trained yet,” said Wenger.”It’s unbelievable and unpredictable and we are hit hard in a position where we need to be strong on Saturday. We have to find solutions and hopefully I can find those solutions.”Per Mertesacker came on for Gabriel for his first action of the season against Everton and look set for a place in Saturday’s final squad.