They have conceded just five league goals so far, with the centre-back pairing of Aymeric Laporte and John Stones proving formidable.
Guardiola joined City on a three-year deal in the summer of 2016 and penned a two-year contract extension in May.
There is also doubt over whether the Portugal global will be available for Tuesday's Champions League clash at Lyon.
Fellaini, though, is refusing to dwell on his side's defeat, and when asked if the result proved the significant gulf in quality between the two sides, the Belgian told Sky Sports : "I don't think so". Sometimes they are accomplished and sometimes not.
"I love to read, but I don't read".
"Maybe I will change my mind later but I am fully convinced in my mind here".
City resume their campaign after the worldwide break against West Ham United and former manager Manuel Pellegrini at the London Stadium on Saturday (Nov 24).
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Guardiola also heaped praise on former City manager Manuel Pellegrini, who will face his old employers for the first time at the London Stadium.
He said: "His career speaks for itself in terms of quality".
'At Villarreal he was incredible.
"It's very hard to win the Premier League again, but I think we have a good team".
Here, we look at some of the top football transfer stories from the British and world media in The Sport Review's Grapevine, published every day in the build-up to the 2019 January transfer window.
"Here he won the league and helped this club be where we are right now".
The squad is back in training as they ramp up preparations for their match against West Ham this weekend!