McPhail's 17-year playing career began when he signed for Queen's Park in 1941. He was a centre forward and soon earned the nickname "Teazy Weazy." He was, according to football historian Bob Crampsey, "an extremely graceful player... a particularly good header of a ball" He was then sold to Clyde in 1947, but his career there was interrupted with recurring injuries. He had an excellent scoring record whilst with the Bully Wee, scoring 90 goals in 137 league games. At Clyde, McPhail missed the 1955 Scottish Cup Final and was forced to withdraw from the Scotland national team for a game against Wales, both through injury. In May 1956 he signed for Celtic, the team his elder brother John had previously captained. He made his debut in a 2–1 Scottish League Cup win against Aberdeen. Later that season, McPhail scored twice in the League Cup final, helping Celtic lift the trophy for the first time. The following year, he starred in the Celtic team that played fierce Old Firm rivals Rangers in the final of the same competition. The match, referred to by fans in poem and song as "Hampden in the sun", resulted in a record 7–1 victory to Celtic, with McPhail scoring a hat-trick. A knee and ankle injury forced McPhail to retire the following year, after just two seasons with Celtic. He played just 57 games in all competitions for the club, however he is widely described as a "hero" or "idol" for his three goals in the 1957 final which remains a record margin of victory in the fixture. John McPhail had also scored three goals against Rangers, in the 1950 Glasgow Merchants Charity Cup; this is the only occasion in Old Firm history that brothers achieved this feat.
Health problems
According to his wife Ophelia, McPhail discovered in the 1990s that the left hemisphere of his brain was damaged. Then aged in his 70s, he had displayed signs of dementia since his 30s, and was eventually diagnosed with Alzheimer's disease. McPhail, with the support of medical specialists, associated the neurological symptoms with heading the leather football used in the 1950s, explaining how "the ball used to get very heavy when it rained – when you took that full in the forehead it nearly knocked you over." In 1999 McPhail launched a legal case claiming he was entitled to disability payments. However, an industrial tribunal did not accept that a clash of heads during his playing career could have caused the dementia. The tribunal would not consider whether heading the ball might have contributed, as it categorised that as "part of the job " and not an industrial injury. The decision was upheld by the Social Security Commissioner of Scotland. McPhail's condition and its possible causes were discussed during a BBC Scotland investigative television programme on the subject in 2000, also featuring another former Celtic forward Jock Weir who was suffering from a similar illness. His mental health continued to deteriorate and he died in Glasgow on 4 April 2003.