Sacking Guardiola will be a poor decision because this is only the first time his team has struggled this much so if the team doesn't trust him in a time like this, it means they don't deserve him. As you said, it's difficult to explain what is really wrong with them, but we have to remember that Rodri was not the only player he missed. He was without KDB, Doku, Grelish, Ake, Dias, and Stones at a certain point in this season.
I believe with a few players in strategic positions Pep can get his team back to winning ways. Players like Walker and Gundugan have failed to live up to expectation so people shouldn't regard them as top players. KDB has been too injury prone to be at top level. Worst of all, Pep's system relies on a DM and without a reliable DM they'll struggle.
I don't think anyone in Manchester City thinking about this because just few weeks back they extend his contract for 2 years so now talking or thinking about sacking is completely out of way they also understand this is not coach level problem they need to fix their squad which is going to happen in January now they have time for settling with next game in Champions League against PSG is important for them if they fail to bring them on level then things can go badly down even out of content.
Just few players and all will be back as mentioned few players fail to give their best so they are facing this time hopefully now we will have things could be fixed with the arrival of suitable replacements which will give confidence back to this team for having success even now titles challenge is not easy but still we can have their nature game for having top spots.