As reported by BBC Sport, earlier on Friday the Football Association confirmed they had launched an investigation after Derby said a Leeds staff member was caught outside their training ground acting suspiciously.
In the buildup to the game, Bielsa was asked about the spying allegations and offered a candid explanation of the incident, per Sky Sports (h/t James Whaling of the Daily Mirror):
"I am responsible for this incident. It's not about being legal or illegal or right or wrong. Yesterday I talked to Frank Lampard and he told me I didn't respect the club.
"I have my view but what is important is what Lampard and Derby think. I'm responsible for it and didn't ask the permission of Leeds United to do it. I have been using this practice since the qualifications of the World Cup in Argentina. It is not illegal and we have talked about it publicly and in the press."
Here's what Bielsa had to say to Sky Sports in full ahead of the second-tier clash at Elland Road:
Derby manager Frank Lampard made it clear he wasn't happy about what had happened:
On Thursday, the Derby Response Unit posted on social media they had responded to reports of a person at the Rams' training complex:
Derby Response Unit - Derbyshire Constabulary @DerbyResponse
Officers have just attended the Training Ground for @dcfcofficial After a suspicious male was seen at the perimeter fence. Excellent searching conducted & male was located. All checks above board! Keeping the team safe to bring home a win against #LUFC on 11th! #SpyingIsCheating https://t.co/a12Zj8gISX
According to John Percy and Matt Law of the Daily Telegraph, the man in question was caught with binoculars, a change of clothes and pliers. The latter were reportedly used to force entry into the complex, which is covered by CCTV.
Leeds also published a statement responding to the situation, which acknowledged the wrongdoing and appeared to suggest Bielsa will be discouraged from similar practices in future, via journalist Henry Winter:
In an article from The National by Ian Hawkley from 2010, it's suggested Bielsa recruited a boy from his daughter's class at school to check out opponents after the youngster said he knew everything about the game.
"Bielsa took him aside, shut him in a room and grilled him about the game, asking questions with increasingly more obscure answers until he was satisfied the youth knew his stuff," Hawkley wrote. "He then asked him to spy on future opponents, and the lad, known as Paqui, was apparently known to climb trees to monitor rivals' training sessions."
Law was critical of Bielsa's practice on Twitter and believes other managers would face more scrutiny in similar circumstances:
The incident is a blemish on what has been shaping up as a season to remember for Leeds, as they seek to get back into the Premier League for the first time since their relegation in 2004. They are top of the Championship ahead of Week 27, two points clear of Norwich City.
Derby are also chasing promotion and are currently on course for a playoff spot, as they sit in sixth in the standings.