Mateu Lahoz, 44, gave Guardiola his marching orders after being confronted by the City boss for mistakenly disallowing a goal against Liverpool at the quarter-final stage in 2018.
The Catalan confronted the Valencia-born whistleblower at half-time after he ruled out a Leroy Sane strike after the ball had been played to the winger by Liverpool’s James Milner.
City were winning 1-0 at the time as they attempted to overturn a 3-0 first-leg deficit.
They eventually lost the tie 2-1, with Guardiola sat in the stand and assistant Mikel Arteta giving instructions on the touchline.
The City manager said: “I didn’t insult him, I was polite, I was correct.
But Mateu Lahoz is a special guy, he likes to be different, he likes to be special.
City have also had other controversies with Mateu Lahoz.
In 2017, he failed to give a penalty for a foul by Monaco keeper Danijel Subasic on Sergio Aguero.
Subasic should have also been sent off, but it was City’s Argentine striker who was shown a yellow card for diving.
And although City won the tie 5-3 after Radamel Falcao had a controversial penalty saved by Willy Caballero, they went out on away goals after losing the second leg.
In October 2017, Mateu Lahoz awarded two penalties to Napoli during City’s 2-1 group stage victory over the Italians at the Etihad.
Mateu Lahoz has twice been put in charge of Chelsea games.
In 2014, the Blues won 1-0 at Sporting Lisbon and the following year they lost 2-1 at Porto.