Manager Roberto Mancini implored his players not to feel sorry for themselves in his pregame notes, with the loss of their title five games before the end of the season a likely source of regret.
For the last month now, the Blues have been the best side in the Premier League.
"We had the control of the game, we dominated for 90 minutes -- we were unlucky to concede that goal at the end," City defender Pablo Zabaleta said. "We should defend better but it's three points. We need to keep going."
Yet their dominance has come far too late.
Few teams are capable of the move that brought Aguero their opener.
Nasri crossed low to the near post, where Aguero turned home his 15th goal of the season.
It was brilliant stuff, if simple in its execution.
But where was this form at Southampton, Sunderland, QPR or any of the other random venues where the Blues have inexplicably dropped precious points?
"We have probably been a bit inconsistent this year, not like last season, and probably that has cost us the title," Zabaleta said. "But we are working to improve, keep winning trophies and we have the cup final at Wembley.
"It is always special to win that competition as well, so we'll try to come back stronger next year and try to win the title back."
City nearly made it two almost immediately as Jussi Jaaskelainen failed to hold Nasri's 20-yard strike and Zabaleta closed in.
The Argentina star seems certain to be named in the PFA Premier League team of the year on Sunday and nearly portended the occasion with a goal.
Jaaskelainen later redeemed himself, turning away Zabaleta's shot from point blank range. Other than that, the first-half was a fairly lackluster affair.
Hart had gone down with an injury a couple of minutes earlier and still seemed to be bothered by it as he inexplicably allowed Carroll's shot to roll through his legs.
Mancini played down fears about Hart. When asked if the goalkeeper was OK, the Italian responded: "I think so."
Mancini said it is important to begin his summer recruitment early but insists he will maintain focus on the rest of this season.
"Now it is important to finish well in this championship," he added. "We want to win the next game and keep hold of the second position and try to win the FA (Cup) final."
On his summer activity, Mancini added: "I think that it's important to move quickly. I think here are a lot of teams that want to buy new players; Barca, Real Madrid, Bayern Munich, Manchester United, we need to move quickly."
Returning after three matches out with a hamstring injury, Silva did his best to prompt City into life, setting Aguero up with a chance he would normally have buried but instead scuffed into the ground and onto a post.
For its part, West Ham played like a side whose return to the top flight has been consolidated by a secure mid-table finish.
It did not prevent Sam Allardyce blowing his top at the fourth official when referee Howard Webb opted not to allow the Hammers to retake a free kick he appeared to be preventing but the visitors took anyway, only for Matt Jarvis to be immediately flagged offside.
Allardyce was left to rue his side's lack of cutting edge as he saw them beaten by two top quality finishes.
"I was just concerned about the players over-respecting the opposition in the first half and having plenty of possession but just giving it straight back and sitting in," Allardyce said. "We had to improve on that from the very start of that second half and we got in their final third and we persisted to do that throughout the whole of the game.
"But as our problem has been all season, as we know, is creating chances and not enough goals scored."
The opportunity had been provided by a superb piece of skill from Nasri, who like so many in blue, failed to reach the heights on a consistent basis this season.
Silva is another, Aguero also.
Yet the Argentina forward set up compatriot Tevez with an astute cut-back, only for Joey O'Brien's last-ditch tackle to deny the hosts.
Tevez turned provider for Nasri shortly afterwards, but with the goal gaping the man who left Arsenal two years ago and won a title at the first time of asking attempted to prod home with his right foot and missed the ball altogether.
On the touchline, Mancini's face was a picture as he slumped into his seat.
Frustration turned to elation 10 minutes from time as Toure provided another moment of magic, creating space for himself on the edge of the area before smacking a clinical effort into the top corner. In its own way, it was as wonderful as City's opener.
And City nearly added further gloss to their day when Aguero was inches away after turning home the loose ball after Jaaskelainen had parried Zabaleta's shot.
Information from Press Association was used in this report.