It was the sort of mistake which, when you are in the midst of a brutal title fight and already facing up to the prospect of a damaging defeat, just cannot happen. Rangers it must be said, going down 2-1 to their Old Firm rivals as Celtic moved to within touching distance of another season of Scottish Premiership success, certainly made a fist of it during a tense second half at Parkhead. But their chances of a much-needed win on the road became, if not entirely impossible, then highly improbable once one of Philippe Clement‘s most trusted lieutenants exited the battlefield. John Lundstram had…