Leroy Sane's second-half winner last Thursday ended Liverpool's unbeaten start to the season and saw defending champions City move four points behind Jurgen Klopp's league leaders.
Some Liverpool supporters claimed the grass at the Etihad was not as short as usual and thus had a negative impact on the Reds' attacking play.
But Guardiola said he has never been involved in discussions over pitch conditions for City's home games.
"I am not a greenkeeper. I never did [request longer grass]," Guardiola told a news conference. "So Liverpool want to play quick, we want to play quicker. So never, never we manipulate it.
"Always we try to put water [on the pitch], here it is not necessary because of the weather conditions and it rains a lot. But I would not suspect that, never, never. We want to try to put the field, always in my career as a manager, in the best conditions for both teams.
"I never made a trick about that. Normally when this kind of thing happens, in the end, I don't know if this is karma or something like that, it always punishes you. So you have to do the best for the opponent for the game, you have to respect our game and our rules.
"Win the game on the pitch, with the rules for everybody."
Pressed again on the accusation, Guardiola added: "I never speak with the groundsman.
"I have many issues in my head, to talk about, to think about the grass, I trust my greenkeepers with what they do.
"But we put the grass in the best condition for both teams. I never make a phone call to say, 'Do these kinds of things to damage our opponents.'
"We always try to win in the same way against our opponents."
City have been without Benjamin Mendy since mid-November due to a knee issue, but Guardiola expects the France international to soon be ready to return to action.
"He is much better, training already," Guardiola said of the left-back ahead of Wednesday's Carabao Cup semi-final first leg at home to Burton Albion.
"Not with the team, alone, but on the pitch. In two or three weeks, maybe he will be with us. Everybody else is fit."