Manuel Pellegrini's side were out-played in every department in the 2-0 defeat at Stoke in which Marko Arnautovic scored twice from assists from the excellent Xherdan Shaqiri and could easily have had a couple more at a windswept Britannia Stadium.
City's defence have recorded just two clean sheets in the last 18 matches, after not conceding a goal in their opening five games of the season, and it is no coincidence the absence of captain Vincent Kompany to injury has affected their stability at the back.
But Hart, returning to the side after injury himself and captaining in the absence of Kompany, believes they have enough quality to cope without the influential Belgium international.
"We've got a great squad and Vinny is a massive part of it but Nico (Otamendi), Martin (Demichelis) and Manga (Eliaquim Mangala - suspended for the Stoke game) are good centre-halves," Hart said.
"After a 2-0 loss it's probably easy to say [Kompany was missed] but we'll stick together as a squad, work for each other and get through this."
A fourth away game without a win, and the third in a row on the road without a goal, has seen City overtaken by Leicester and Arsenal at the top of the Premier League.
Hart admits they have to raise their game, starting on Tuesday when they host Borussia Munchengladbach needing a win and a favour from Sevilla to top their Champions League group, from which they have already qualified, to give them a much-needed easier quarter-final draw.
"At the level we're playing at, we need to turn out performances of seven out of 10 at least every week and rely on some players to produce eights and nines," Hart said.
"That's how we should be playing and we're not. Credit to Stoke, I thought they deserved to win.
"It was a disappointing start (conceding after just seven minutes) and we couldn't recover from it. We didn't play well.
"Conditions were tough but that's English football, I said before the game no-one would be able to walk of the pitch with an excuse.
"It's not like the wind got up four seconds before kick-off, we knew what we were coming into and Stoke knew what they were coming in to.
"A few of the lads are feeling it from the amount of games we're playing but that's not an excuse."
Defender Nicolas Otamendi, who has looked relatively comfortable in central defence alongside Kompany or Mangala but was shaky paired with Demichelis, believes they lacked the necessary attitude to win at the Britannia.
"Obviously the conditions didn't suit the way we play but we can't honestly use that as an excuse," he said.
"We may have lacked a bit of attitude on the pitch but we must look to the next game. We need to show a better impression.
"We didn't perform well but the team always fights and we'll get a good result next time.
"Credit to Stoke, they are strong at home and the conditions suited their style of play and they had a good performance.
"Things didn't go as we expected. We will now look forward to the next game, try to get three points and forget about this game.
"We need to keep working hard. We need to keep focused defensively and we need to work hard to amend these errors."