Man City obviously huge favourites, but they showed signs of weakness in their last game.
You can not compare West Ham to Aston Villa, West Ham vie for Europa League or Europa Conference League unlike Aston Villa that has nothing to vie for and not also planning to leave relegation and not among the relegating team.
It's certainly a valid point that Villa have nothing left to play for, yes. But I suppose that could work both ways - there's no pressure on them, and that can often free a team up to play better.
My point wasn't really about West Ham playing well though, it was more about Man City starting to show some nerves and be less good than they usually are. West Ham are better than Villa, but you'd normally expect Man City to beat both of them easily. The fact that they struggled against West Ham means they might struggle again in the next game, even if the opposition is not quite so good.
I don't want to call any team in the Premier League weak. They often surprise everyone by winning against big teams. However, Manchester City's performance against Aston Villa is very good. The city has won the last 5 matches against Villa. So naturally we think that Manchester City will win. However, if the players of Manchester City make any mistake, the players of Aston Villa will take the opportunity very well. And so Manchester City defenders have to perform very carefully.