Moyes has played with three centre-halves for most of 2017 but returned to a back four for the trip to Everton last weekend.
Jason Denayer was a last-minute absentee from the 2-0 defeat at Goodison Park after waking up with an illness on the morning of the game, but the Sunderland boss has revealed that he would been deployed in a midfield three if he had been fit.
Moyes said: “I was going to play a back four against Everton. Jason would have played as a midfield player. What I did have was the ability to slide into a back five if we needed it.
“We have played it and had a couple of good results, I think it is something we can move in or out of.
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“I didn’t think it was suited to that game, which isn’t to say that it isn’t suited to this game. We could play Joleon (Lescott), we could use Billy Jones as a third centre-back, and obviously Papy’s returning as well.”
Moyes will now weigh up whether to continue that formation against City or return to the reinforced defence.
Djiolobodji’s return from suspension gives him another option to play alongside John O’Shea and Lamine Kone, but the Scot has hinted that a back four may be better suited.
City are likely to play with a single striker and, with Pep Guardiola’s side posing such a threat in the wide areas, Moyes feels he may need more players in advanced positions to defend from the front.
Moyes said: “We played Liverpool with four at the back, so we’ve chopped and changed a bit.
“The difficulty is the way Man City play, with two out-and-out wingers. We could get pinned back if we don’t try and stop them further up the pitch.
“We might have three centre-backs looking at one forward, so we need to think about it.
“Between now and the end of the season, I do think we’ll have to play both systems to give ourselves a chance.”
Moyes was in the stands to watch Manchester City hammer Huddersfield in midweek, so knows he faces a big challenge.
However, he is hopeful that he will be able to find a way to negate the gap in quality.
The Scot said: “With the distance in level and quality of the players, my job is to try and reduce that as much as I can, whether through tactics or way we play.
“We don’t have the same budget as Manchester City, we’re not buying on the same level as them.
“How we reduce the quality of their players is a big question.”