As long as there are still replacement players for the line usually occupied by John Stones and Kyle Walker, I don't think Manchester City will immediately become weak because of this. Because the Manchester City coach himself will also think about this more seriously because remembering that the match is at Manchester City's home ground, the Manchester City coach will choose players who are more suitable to fill that line so that the match can be exciting and it won't be easy for Arsenal to win there.
I don't know the coach of Manchester city to be weak minded or been our of idea about what to do or how well to handle his boys, he's always got this mindset of not letting his team best room dependent on a single players such that they will end up loosing their form or wouldn't be productive in the absence of the players, he trys to build a team thats dependent on a collective team strength and that's made him stand out.
The absence of any of these players will only mean to guardiola to make replacement and the team moves on, it may actually affect the strength of the team slightly buy or wouldn't be for room long and they will be back again in form on their feet doing so well so it's more like they are just going to have a slight effect on productivity buy it's not a total halt on their productivity, just like in the case of de bruyne, when he was away for awhile it was only affecting the number of goals they could get in a game.but they were still on winning ways and winning most of their games.
Kyle walker has got a replacement already if he's absent and guardilola knows roo well the implications of his absence and wouldn't take chances so he's know how best to tackle the situation and still keep his team ahead regardless of the situation so I doubt if Manchester city will actually be really affected because already they have built that very strong form for this season already and their mentality is more of winning than otherwise.