Twenty years ago, Mo Johnston, now manager and technical director of Toronto FC, made one of the most controversial transfers in the history of the sport. After growing up a Celtic fan in Glasgow and starring for the club from 1984 to 1987, Johnston signed for crosstown archrivals Rangers in 1989, after a stint in France. Collectively called the Old Firm, the two clubs have a deep history of sectarian separation and violence. Glasgow is historically Catholic, Rangers is historically Protestant.

Johnston wasn’t the first Catholic to sign with Rangers, but he was the most high profile at a time when the club was trying to overcome its sectarian reputation by signing players regardless of their religion. Celtic fans, who had adoringly called Johnston MoJo, now labeled him Judas. On the Rangers side, some fans tore up season’s tickets and burned scarves after their Protestant club signed a high-profile Catholic. Death threats and a 24-hour security detail followed.

Johnston says he knew the implications of the move before he made it as a 26-year-old. “I felt it had to be done. I felt the barriers had to be broken,” he said. “And, to be honest with you, it was difficult at first but when teammates and fans start to embrace you then it becomes a lot easier.” And although Johnston shirks questions about the religious roots of the rivalry, he gladly talks about what playing soccer for two such historic clubs meant. “There are many happy moments on both occasions,” Johnston said of winning league championships and being named player of the year with each team. “It’s special being part of an organization that’s synonymous with world soccer. If you look at the history and the background of both clubs, it was a true honour to be part of both.” Now a 46-year old parent of four, Johnston has twin 9-year-old boys; one supports Celtic while the other opted for Rangers.