The title-chasing Blues have been shut-out in successive outings by Chelsea and Norwich City.
The Canaries were given little chance of picking up a clean sheet ahead of their meeting at Carrow Road on Saturday, but they were rarely troubled during a goalless draw.
City saw more of the ball in Norfolk and had plenty of efforts on goal, but few troubled Canaries goalkeeper John Ruddy.
It was a similar story against Chelsea in their last outing, as they went down 1-0 at the Etihad Stadium, and Pellegrini admits he needs to find a way of righting those wrongs.
He told Sky Sports: "First of all, I think Norwich played very well at defending. We could have scored a goal, we had some chances, but they did very well."
On the response offered to the Chelsea setback, the Chilean added: "A defeat will always bring disappointment but the most important thing at this moment is that we are with players who are not 100 per cent fit, that's a problem.
"We have seen that with the strikers - Sergio Aguero, we saw the other day that Alvaro Negredo is not 100 per cent, and Edin Dzeko the same thing.
"Today we tried but it's not easy to score goals. Everyone talks about the amount of goals we score, but it is very difficult to score goals.
"Maybe it was the same mistake that we had when we played against Chelsea, we had a lot of shots but not a lot on target."
A stalemate on the road prevented City from reclaiming top spot in the Premier League table, but Pellegrini remains pleased with the position his side are in with 13 games to come.
He added: "We react in the way that we must do it. We have 39 points, we are two points behind the leaders, exactly the same as last week.
"There are a lot more games, for all the teams, not just us. We must keep fighting and try to continue playing the way we did two weeks ago."