The late John Morrison was built to take a shoulder charge. When Paul ‘Pillar’ Caffrey, the Dublin football manager in 2006, caught the Mayo selector unawares, Morrison lost his bearings for the briefest of moments, before the Armagh native steadied himself and offered a wry smile. Ciarán Whelan, seconds before had led the Dublin players towards Hill 16, visibly perturbed by Mayo’s antics. It was the All-Ireland Semi-Final. It was the genesis of a rivalry. The context was the temerity of Mayo to warm-up in front of the Hill; sacredly reserved for Dublin when playing at Croke Park. In the…