CANTERBURY Crusaders scrumhalf Justin Marshall and lock Norm Maxwell have been ruled out of Saturday night’s Super 12 rugby semi-final against the Otago Highlanders in Christchurch. Both suffered calf muscle tears in training this week and were ruled out by medical staff after a fitness test. Ben Hurst will replace Marshall, while Chris Jack will replace Maxwell. In another blow, flyhalf Andrew Mehrtens is in doubt for Saturday’s game after leaving Thursday’s training early, suffering from a back complaint. Should Mehrtens be ruled out, Aaron Mauger will be called in to replace him.