City had Josko Gvardiol, Ruben Dias and John Stones missing from the backline, with none of the trio expected to return to action until at least next month.
It had forced Guardiola to recall academy product Max Alleyne from his loan spell at Watford. The 20-year-old was given his first-team debut on a cold evening in the cauldron of the top flight.
Alleyne performed admirably on the big stage and it is not his fault he has been thrown into this in such circumstances, just as Nico O'Reilly was brought in to the set-up because of last season's injury crisis.
In the end, Erling Haaland's 150th goal for the club mattered little as they have conspired to drop six points in a week, giving a major boost to Arsenal.
With Aston Villa also drawing, Mikel Arteta's men have a golden opportunity to go eight points clear - a scenario they could only have dreamed of just last week.
"If you don't win games, we cannot think about these things," Guardiola said of the title race. "We had an incredible result Nottingham Forest [in City's final game of 2025] and after we played three games and we played really well.
"They have momentum, Brighton move really well, except the first five to 10 minutes we did really well in general and maybe the first half a little bit less - in the last 15-20 minutes we had incredible chances.
"Expected goals doesn't give me anything. It's how you play for goals and we could not do that today."
Former Manchester United defender Gary Neville said on Sky Sports: "It feels like a big week. Manchester City drawing at home to Brighton, it feels like another punch in the ribs.
"Arsenal will be going to bed tonight, ahead of a big game tomorrow night against Liverpool, very confident of where they are at right now."
Guardiola also appears to be showing the stress that goes with dropping more points in the title race, clashing with Brighton boss Fabian Hurzeler on the touchline.
The German said "emotions are part of the football game", while the City boss said it was "absolutely" fine between the pair.
City winger Jeremy Doku added: "I think a draw at home is never really a good point. We are not that happy and would've preferred three points.
"We don't really look at the table. We try to be ourselves and score more goals."