He signed for United on leaving school in 1950 and made his first team debut in the Football League First Division against Middlesbrough on 6 December 1952, at the age of 17, and by the age of 20 he was a regular member of the first team.

He was the club's first-choice outside left until the final few months before the disaster (when he was displaced by Albert Scanlon) and had collected two League Championship winner's medals in the two seasons leading up to the Munich air disaster.

His performance against Real Madrid in the 1956-57 semi-finals reportedly inspired the Spanish giants to sign a new right-back specifically to combat Pegg's talents in the future, although his death less than a year later meant that he never played against them again.

Pegg's sister, Irene Beevers, contributed to a 1998 ITV documentary, The Busby Babes: End of a Dream, which commemorated the 40th anniversary of the tragedy.

She, Pegg's brother and Pegg's other sister, Doreen Robinson (who now lives in Australia) visited the scene of the Munich air crash in September 2005, on what would have been his 70th birthday, to pay tribute to their brother.