Southport, Lancashire born inside forward Lionel Watson began his football career with Laurel Rovers of Southport in 1898, and played for High Park in 1899 before joining hometown professional club Southport Central in 1900, from where he was signed by First Division Manchester City on amateur forms in 1901. He made his Football League debut, and sole appearance for City, at Sheffield United in November 1901, and joined Blackburn Rovers in the 1902 close season. He was a regular in their 1903-04 campaign, top scoring for the club with 15 goals, but failed to make the same impact in 1904-05 and joined Southern League West Ham United in the summer of 1905 after 19 goals in 61 appearances for Rovers.
He made his debut against Swindon Town on the opening day of the 1905-06 season, and scored hat-tricks for The Irons in a 5-1 victory over Luton Town in September 1906, and in a 4-1 win at Fulham in December 1906, scoring 27 goals in 80 appearances over his three seasons at Upton Park. He returned to Football League action in the summer of 1908 joining Second Division Blackpool, but played only once at Grimsby Town that December before retirement.