In 1990, Gallagher was one of the first of a succession of
All Blacks to switch codes to rugby league, following his understudy
Matthew Ridge, who signed with the
NSWRL's
Manly-Warringah Sea Eagles only a week before. Other All Blacks who followed soon after were
Frano Botica (
Wigan),
John Schuster (
Newcastle Knights) and two years later
Va'aiga Tuigamala (Wigan). He was initially signed by
David Ward for
Leeds. He was considered one of the fastest players over 30m when he switched to league, and this was put to good early use by Leeds. He was targeted by opposition players in defence and was badly injured in an alleged
spear tackle, playing away at
St Helens involving
Tea Ropati. He may also have found the tactical differences between the two codes difficult to adjust to, particularly in his favoured full-back position and the move was unsuccessful. Perhaps his finest moment for Leeds came in a match against
Australia during the Australian teams
1990 Kangaroo tour when he scored the opening try of the game at
Headingley. Gallagher's defense came into question later in that game when giant Kangaroo second rower
Paul Sironen scored two tries, both times running over the top of him. Following the signings of fullbacks
Morvin Edwards and
Alan Tait in the
1991–92 season, Gallagher lost his place in the first team. Gallagher signed a three-year contract for the
London Crusaders in July 1993, and played for one season. ==Return to rugby union==