The Premier League champions were knocked out of the fourth round of the FA Cup by the Championship side after playing Hamburg in the UAE during the week.
City only returned to the UK on Friday but their manager has refused to blame the midweek game for their eventual loss at the Etihad.
"No, I don't think so," he told BBC Sport when asked if he thought the game in Abu Dhabi had tired his team out.
"It's easy to have an excuse, but I don't think that was the case."
Instead, the Chilean conceded that Aitor Karanka’s outfit deserved their win, as goals from Chelsea loanee Patrick Bamford and Kike saw them to a 2-0 win. Now, the manager will instead turn his attention to chasing down Premier League leaders Chelsea and going as far as possible in the Champions League.
City take on Chelsea next Saturday and are currently five points behind Jose Mourinho’s team in second following their loss to Arsenal last Sunday. They are also set to take on Barcelona in the last 16 of the Champions League in the middle of February in what will no doubt prove a difficult tie for Pellegrini’s side.
"They are a team who work well; that's why they are second in the Championship. They had opportunities to score more goals and deserved to go through,” added Pellegrini.
"Now we must continue in the Premier League and Champions League. I wanted to continue in all the competitions but now we must focus on the Premier League and Champions League.”