Leeds extended their lead at the top of the Championship with a 2-0 win over Derby tonight, but victory was marred by manager Marcelo Bielsa's admission he was responsible for a spying scandal that left Derby boss Frank Lampard furious.
Derby County released a statement earlier on Friday saying police had been called to their training ground on Thursday to investigate an intruder "acting suspiciously".
Bielsa, who has enjoyed a storied career in charge of Argentina, Chile and a host of European clubs, claimed he had used the practice of spying on opposition's training sessions for nearly 20 years dating back to Argentina's qualifying campaign for the 2002 World Cup.
"It's true there was someone from Leeds United," the Argentine told Sky Sports. "The responsibility for this lies with me. I'm responsible. It doesn't matter if it's legal or illegal, or right or wrong. For me it's enough that Frank Lampard and Derby County feel it was not the right thing to do and that I didn't behave well.
"I didn't ask permission from Leeds United to do it so it's my responsibility. "Without trying to find a justification, I've been using this kind of practice since the qualifications for the World Cup with Argentina."
On the field Leeds snapped a three-game losing streak with a dominant display as goals either side of half-time from Kemar Roofe and Jack Harrison opened up a five-point lead over Norwich and a seven-point cushion in the race for automatic promotion.
However, Lampard believes Leeds could face a sanction if Bielsa has been spying on the opposition all season.
"He's admitted it so it's easily dealt with. It's up to the league to see how they deal with it. Obviously, it's not just Derby County. We had somebody the day before our first game against them which we lost 4-1. Leeds can beat you 4-1, they are a fantastic team, but we had someone in the bushes so that's twice this season now."
Lampard and Bielsa shook hands before the match, but the former England and Chelsea midfielder believes his counterpart was guilty of unsportsmanlike conduct and refused to accept cultural differences as an excuse.
"At least, on a sportsman's level, it's bad in my opinion," added Lampard. "If we're going to start talking about 'culturally, I did it somewhere else' - that doesn't work for me. If I'm lucky enough to do well and travel to another country I'll find out what the etiquette is in that country and abide by that."
"It's disrupted our build-up to this game. People are going to say I'm trying to make an excuse, but I'm going to speak like this after the game - win, lose or draw."