He played for Middlesbrough, York City and Hartlepool United making a total of 339 league appearances, scoring 32 goals.
On leaving school he worked as a plasterer and played football for the east Belfast part-time side Dundela F.C.
During his time at Sheffield he played nine games and scored six goals in a struggling Wednesday side who were relegated to Division Three at the end of the season.
At the end of the loan spell, McMordie could not agree terms for a full transfer to Wednesday and returned to Middlesbrough.
He signed for Hartlepool United in December 1976, making 47 league appearances before deciding to retire early in the 1978–79 season, shortly after his 32nd birthday.