Derby caught a man lurking at their practice on Thursday, and the stranger was later confirmed to be a Leeds employee. Rams boss Frank Lampard was said to be concerned with the security breach and the FA stated they would open an investigation.
That may not be necessary, however. Speaking to Sky ahead of the clubs' Championship meeting on Friday, Bielsa openly admitted to surveilling the Rams' training and revealed he often uses this method.
"It's true, there was someone from Leeds there," the Argentine said through an interpreter, according to The Guardian's Niall McVeigh. "The responsibility for this incident is mine. It doesn’t matter if this is legal or illegal, right or wrong ... for me, it's enough that Frank Lampard and Derby County were unhappy, to show that I didn't behave well. Yesterday, I talked to Frank and he told me I didn't respect his club. I have a different point of view, but the important thing is what he and Derby think.
"I'm the only one responsible for it, I didn't ask Leeds for permission to do that. I've been using this kind of practice since the (2002) World Cup qualifiers with Argentina. This is not unlawful, we've done it publicly, we talk about it in the press. For some people, it's the wrong thing to do - for others, it's not."
Certainly, Lampard is unimpressed. The former midfielder even suggested this was not the first time this season his side have been on the receiving end of underhand dealings from Bielsa and his staff.
"On a sporting level, it's bad, in my opinion," Lampard said. "Talking about 'I did it somewhere else, it's fine' - that doesn't work for me. It's disrupted our preparations. Police had to come to the training ground, so that was disruptive.
"We were training on team tactics, shape, personnel, and the fact that Harry Wilson wasn't training. He's admitted it, so I don't think there'll be any further action - but we had a guy in the bushes before we played Leeds earlier this season, and we lost 4-1."
Bielsa's Leeds overcame Lampard's Derby by a 2-0 scoreline at Elland Road on Friday, fluffing up the West Yorkshire club's cushion atop the Championship to five points.