City face a monumental challenge at the Nou Camp on Wednesday as they bid to reach the Champions League quarter-finals by overturning a 2-0 deficit against the Spanish champions.
They will hardly travel in the best of moods, having been instantly brought back to earth following their Capital One Cup success by old adversaries Wigan.
The Latics repeated last year's shock FA Cup final victory over City by securing an equally unlikely 2-1 win in their quarter-final clash at the Etihad Stadium.
Pellegrini called for his side to immediately refocus and keep the club in the hunt for more silverware this season.
The Chilean said: "I think we all work together, we all have a responsibility to win.
"We finished one trophy and we won that. Now we have to continue playing the Champions League and Premier League.
"We have a lot of things to fight for until the end of the season.
"First we must try to win in Barcelona and then continue to try to reach the top of the table with the three games we have in hand.
"We must react. We still have a possibility. We will try to do a very good game and we will see what happens against Barcelona.
"Winning always gives you confidence but maybe a game like this can bring a reaction from the team. It could be positive."
City failed to respond to the high-energy and fully-committed approach Wigan took to the game.
They fell behind to a Jordi Gomez penalty in the 27th minute after the erratic Martin Demichelis brought down Marc-Antoine Fortune and James Perch doubled Wigan's lead early in the second half.
A triple substitution sparked City into life in the final half-hour and they pulled one back with a low Samir Nasri strike after 68 minutes.
They went on to lay siege to the Wigan goal but they found no way through.
Edin Dzeko, who had earlier hit the post, headed wide and was denied what seemed a certain goal by a remarkable Emmerson Boyce clearance.
Micah Richards also went close and Sergio Aguero tested Scott Carson twice.
Pellegrini felt his side's efforts deserved more but accepted it was not to be.
He said: "The three changes changed the character of the team and that's why, after you lose the game, I think it is difficult to say you are unlucky.
"But I think we at least to deserved the draw as we had three or four chances to score, but it was too late."
On the positive side for City, top scorer Aguero lasted the duration in his second game back after a hamstring injury and should be fit to continue in midweek.
Pellegrini said: "He is now in shape to play the 90 minutes. We needed him and he played the 90 minutes.
"It doesn't have any relation to the game against Barcelona."