If Philippe Clement needed any material to show his Rangers team as they prepare to walk into Celtic Park, Sergio Porrini and the class of 1999 have just provided it. The Belgian manager is tasked with motivating his team to walk into the ‘Lion’s Den’ in little over a week’s time in what could prove a Scottish Premiership title decider. Rangers’ late season slip in an unconvincing five-game run has handed Celtic the title ascendency and realistically the club has to take all three points at Parkhead to rescue the league campaign. It’s not an insurmountable task but Big Phil could certainly use…