Kevin De Bruyne felt Manchester City's final ball let it down as the leader had its perfect start to the Premier League season halted by West Ham.
Manuel Pellegrini's side headed into the Etihad Stadium encounter having lost to Juventus in the UEFA Champions League midweek but on the back of five wins from as many domestic attempts this term.
Victor Moses brilliantly opened the scoring for West Ham and the host was left with a mountain to climb when Diafra Sakho made it 2-0 in the 31st minute.
De Bruyne, making a full debut after his club-record switch from Wolfsburg, reduced the deficit in first-half stoppage time but an inspired display from West Ham goalkeeper Adrian and committed, last-ditch defending helped the visitor survive relentless pressure after the break.
"We tried everything to put pressure on them," the Belgium international told reporters afterwards, as quoted by BBC Sport.
"In the second half they didn't create one good chance. Maybe our last pass wasn't good but we didn't play badly.
"We didn't start well or defend well for their two chances. We have to learn from this."
De Bruyne added that he is settling nicely into life in Manchester and he is keen to rediscover the winning feeling when Pellegrini's men head to Sunderland in the third round of the League Cup on Wednesday.
"I try to do everything today to help the team, but it wasn't enough. I am happy with how I am integrating.
"In a few weeks when I am settled it will be even better for me.
"If you lose these games you have to go on quickly. We tried to have a good reaction after Juventus but now we go on to Tuesday."