Player who injured is definitely will affect the result since the substitute player isn't as good as the main line up, I only talk about the skill while chemistry, strategy etc also give a big effect to other players. Not many teams have a balance main line up and substitute player, I think only Brighton have this, whoever who play, the result will not be different.
Let's see how Brighton faces Manchester City this week at the Etihad Stadium, because currently Manchester City's appearance is starting to look different even though it is still strong enough to win. But if Brighton can beat Manchester City at the Etihad Stadium, this will actually be extraordinary for Brighton because it will continue to create increasingly exciting competition in the Premier League standings table. However, I am also still not sure about Brighton in terms of beating Manchester City at the Etihad Stadium.