Following a period working as a cab driver in London, Byrne decided to try sports massage after seeing a 'help wanted' advertisement placed by Chelsea's team physiotherapist at one of the matches.
In February 1993, roughly six months into Byrne's time with the club, Porterfield was replaced by David Webb who was in turn dismissed in summer 1993 to make way for Glenn Hoddle.
He held the two roles simultaneously under Hoddle for two years, before deciding to devote himself to physiotherapy by enrolling in the Football Association sponsored two-year course for sports injuries, while still working as a masseur at Chelsea where he eventually became the team's assistant physiotherapist.
Byrne's relationship with Beckham intensified during the 1998 FIFA World Cup in France where the masseur became a close confidant to the twenty-three-year-old, helping him cope with the pressures of his first major international tournament.
Byrne became the listening post through the player's World Cup ups and downs, such as not playing in the opening group match against Tunisia or his free-kick goal against Colombia.
Several high-profile signings, such as 30-year-old Ramon Vega and 24-year-old Stephen Hughes, joined in summer 2001 as the wage bills soared, with even Vialli paid close to £1 million a year.
[7] Following Vialli's dismissal, the club's recently appointed chairman, Graham Simpson, promoted Byrne to the post of director of football – a newly created role responsible for player contracts, scouting and the academy.
Watford spent most of the 2002–03 First Division season trying to come up with an acceptable financial model that would allow the club to survive now that TV money was no longer there as a revenue source.
The cash-strapped club narrowly avoided administration in the 2002–03 season by instituting cost-cutting measures such as forcing players and staff to accept a 12% wage deferral and raising funds via a share issue.
Only months earlier, Beckham had left his long-time representative agency SFX to join Simon Fuller's 19 Entertainment that already managed the career of his pop-star wife Victoria.
[16] In July 2007, Beckham made the long-anticipated mid-season switch to Los Angeles with Byrne having played a key role in arranging the transfer six months earlier.
Byrne hired club personnel, ignoring Galaxy's general manager Alexei Lalas, such as bringing Ruud Gullit as head coach in November 2007.
[14] After ending his role as Beckham's personal manager, Byrne confirmed in January 2009 that he was in talks with the Leyton Orient chairman Barry Hearn regarding a possible takeover by the Byrne-headed consortium.
Byrne put together A:3K Football, a skills challenge event with a futuristic gladiator setting at The O2 arena in London on 17 July 2010 with David Villa, Cesc Fabregas, Cristiano Ronaldo, Didier Drogba, Steven Gerrard and Wayne Rooney.