"Mad Marc" to his teammates, began his career at Oldham Athletic before moving through the leagues, eventually joining Bolton Wanderers in June 2013. A tough tackling and no-nonsense full-back, he was brought in to replace the previous incumbent Marcos Alonso who left under freedom of contract to Italian side Fiorentina.
Tierney unfortunately suffered a serious injury at Christmas 2012 having been first choice at Norwich City in the Premiership, and struggled to regain his place following the signing of Spaniard Javier Garrido. He left the club to join Bolton Wanderers once his contract expired at the end of the 2012/13 season.
Eligible for both England and the Republic of Ireland, Tierney is yet to become a full international though it was thought in 2012 that he was on the brink of declaring for the Irish squad ahead of the European Championship tournament, though in the end he was not called up.