I don't think there is any analogy between Real and City now. Real is first in La Liga (with one defeat), and City is 5th in the Premier League (with 4 defeats and 11 points behind the leader).
As for injuries, all teams suffer from them, but somehow cope. The nosedive that City has found itself in is unprecedented.
Real Madrid has only lost one league game this season, but Manchester City has lost four, so I honestly don't think they are on the same level. The best team in the Premier League, which has won the league four times in a row, shouldn't lose four straight league games. Manchester City always suggests their injured players as the reason for their worse performance. With just four injured players, Manchester City is unable to win games, and Real Madrid has six important players injured and still manages to win.
But, in my opinion, Manchester City is playing at its worst right now, the players are exhausted and are unable to play as well as they did in past seasons because they have won the league title four times in a row, and it is difficult for players to win the Premier League four times in a row. Even though the whole of Manchester City's players are back to their best level, I doubt they will become any better to win the league again. They played a lot of games from the previous season, Guardiola has to improve his players at this point to maintain their Champions League position before the end of the season.