The issue of 'Spygate' was first raised ahead of Derby County's visit to Elland Road when a Leeds employee was caught outside the Rams' training ground.

Bielsa faced widespread criticism for his actions - not least from Derby manager Frank Lampard - but, at a hastily arranged press briefing today, the Argentine conceded it was not an isolated incident.

"I observed all the rivals and we watched all the training sessions of the opponents before we played against them," Bielsa said during a detailed presentation on his analyses. 

Leeds issued a statement after the Derby game reminding Bielsa of his responsibilities, while investigations have been launched by the English Football League (EFL) and Football Association (FA).

Bielsa admitted Leeds' next opponent, Stoke, hasn't been as easy to do due dilligence on, owing to a recent managerial change.

Bielsa's explanation of the questionable scouting methods scrutinised during 'Spygate' led the Leeds United boss to reveal how his detailed dossiers once surprised even Pep Guardiola.

The Argentine's renowned dedication to his craft has earned him many admirers including Manchester City manager Guardiola, who discovered the remarkable depth of assessment the 63 year-old undertakes following the Copa del Rey final clash between their respective Athletic Bilbao and Barcelona sides in 2012.

"When I was a coach of Athletic Bilbao we played Barcelona in [the Copa del Rey] final and we lost 3-0," Bielsa said. "[After the match] I gave all the information I had on Barcelona to Pep Guardiola. Guardiola had a look at it and he told me 'you know more about Barcelona than me!'.

"I do this analysis to ease my anxiety, but it was useless information because they scored three goals."

Bielsa's level of research includes watching every game of the other 23 teams in the second tier, in-depth studies of opposition players and statistical breakdowns of favoured formations.

"We watch all the games of 2018-2019 of each opponent," he said. "We watched the 51 games of Derby County. They've played a 4-3-3 [formation] 49.9 per cent of the season... we use this to understand the system and why and when they change the system during a game.

"The analysis of each game takes four hours of work. Why do we do that? Because we think it is professional behaviour."