Manuel Pellegrini felt aggrieved with referee Mike Dean's decision to award a penalty, but admitted his Manchester City side lacked a creative spark in their 2-0 defeat to Arsenal.
A Santi Cazorla spot-kick and Olivier Giroud's second-half header ensured the Premier League champions suffered their first defeat in 15 games at the Etihad Stadium on Sunday.
Cazorla beat Joe Hart from 12 yards after Vincent Kompany was adjudged to have fouled Nacho Monreal in the first half, but Pellegrini felt the full-back went down easily.
The City boss acknowledged that his team were below par and failed to ask enough questions of the Arsenal defence.
He told Sky Sports 1: "There are two principal reasons [for the defeat]: one was the penalty, which changed the game. I don't think it was a penalty, but it was unnecessary [for Kompany] to do it.
"The movement of Kompany allows him [Monreal] to dive. I am not saying it was a bad mistake of the referee. The penalty changed the game, but it was not the reason we lost.
"After that the game changed and we didn't really have any chances to score. We were not a creative team, we didn't have the ideas to cause damage in their defence. We have a lot of time on the ball, but without creativity it is not possible to score goals.
"I always give credit to the team that wins the game. Arsenal played very concentrated. We ran the whole game, pressed very well, but we didn't have the ideas of how to create the space in their defence. I think we are a better team than the way we played."
City are five points adrift of leaders Chelsea and travel to Stamford Bridge for their next Premier League game in a fortnight.
Pellegrini warned Jose Mourinho's side that the champions are capable of pegging them back once again as they attempt to retain their title.
He said: "It is important, because it is a long way to recover the eight points. Now they are five points in front, we have to play against Chelsea and we will try to prepare to win that game and close that gap again.
"We allow Chelsea to be five points in front. I don't think this is finished. With a win or draw we can continue fighting."
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