Betis won 2-1 thanks to Giovani Lo Celso's brace, in a game which proved a grind.
Pellegrini later said: "I don't want to talk only about one match or one team. Between all of us, coaches, players and referees, we have to contribute much more to the spectacle. Of course the result is very important, but with minutes in which there is not much play... In Spain, football is played much better but in terms of spectacle we must improve. The sense of spectacle cannot be lost. We tell the players not to fall into provocations or constant fouls.
"Lo Celso had a great game, as the numbers reflect. We were not sure how many minutes to leave him on for, and after the second goal it was not a good idea to leave him on. He has fit in perfectly with a team that really liked him.
"I don't think the referees are biased, there are statistics and the referees know who wants to stop the game and who doesn't. I find it incredible that we ended the first half with almost the same number of yellow cards.
"We coaches should not get involved in this issue because it would be in our favour, that should be analysed by the press. We do not have to analyse the mistakes of a match because we would not be objective. We need to improve a lot so that in Spain football, even if it is results-oriented, is a spectacle."