The Whites were absolutely dismantled by Manchester City in what was the Premier League champions' best display of the season so far.
It was a performance that demonstrated a timely reminder to Liverpool and Chelsea that they're the team to beat this term.
They hit SEVEN at the Etihad, with Kevin De Bruyne (two), Phil Foden, Jack Grealish, Riyad Mahrez, John Stones and Nathan Ake all getting on the scoresheet to sweep the Yorkshire outfit aside with embarrassing ease.
Guardiola learnt his trade from the legendary Argentine when starting out as a manager.
He was told by Argentina legend Gabriel Batistuta: "If you want to be a coach, you have to get together with this guy."
The Barcelona legend then made the 5,000-mile journey to Rosario to visit Bielsa in 2004, where the pair talked about all things football over a gorgeously well-prepared barbeque - tactics, teams and anecdotes from their respective careers.
Tuesday night's match, however, was a display that proved that the apprentice has really become the master.
Guardiola dealt his managerial icon the biggest defeat of his career and he couldn't hide his admiration for his side's display after the match.
Asked what pleased him about his side, Guardiola told talkSPORT: "The way we played.
"It's been similar the last two months, consistent, the way we are playing is so good.
"Leeds have a specific quality of a player and I'd say that many teams struggle a lot. Chelsea last game, they were fantastic.
"They are the best team in terms of intensity."
Bielsa pulled no punches as he bemoaned his side's worst display since he took charge of the club in 2018.
The Argentinian told BT Sport: "This is the worst performance in the four years. At no moment were we able to balance the game. The sensation we gave off was that anything they attempted we couldn't prevent.
"It's not that City played very well - it's a lot more noticeable how badly we played than how well City played.
"City play like this all the time, or similar to it, but we have never played so badly in these four years."
City have won seven Premier League matches on the bounce and they now sit four points clear of Liverpool, who play Newcastle on Wednesday.
Guardiola's men will be hoping they can make it eight consecutive wins this weekend with a trip to Newcastle up next on Sunday.