Pellegrini insisted he would do “exactly the same again” in terms of his vast rotation, despite accepting the defeat could impact Wednesday’s return leg in Madrid – and dent City’s chances of securing a top-four league finish.
City’s hefty defeat leaves that fourth-place Premier League finish in the balance, with Arsenal and Swansea still to play.
“I would do exactly the same again because we have an important game on Wednesday to play for the Champions League final,” said Pelllegrini.
“We continue in the Premier League in the next two games to be in the top four so that was a risk, but one we also had to take.
“I was very disappointed, especially in the defending. It was the same players who played other games.
“We knew before the game it was a risk but we have to take those risks because we have an important game on Wednesday.
“Maybe if we had played on Saturday we could have put more players in.
“I always say the best way to prepare for the next game is to win and that’s why we did so well before Paris St Germain.”
Pellegrini expects Yaya Toure, Vincent Kompany and Kevin De Bruyne all to be ready for the Madrid trip on Wednesday, with all three not involved at St Mary’s.
Kelechi Iheanacho’s brace could boost his chances of facing Real, but Raheem Sterling failed to further his own cause with an ineffective display.
Pellegrini admitted there were no positives in defeat, and refused to comment on Sterling’s performance, insisting: “I don’t analyse individual players.”