Hampshire batsman Pietersen, who was in Manchester on Monday helping to promote the "Urban Cricket" initiative, has been as shocked as the rest of the country by the news Flintoff needs a second operation on his troublesome left ankle.
Pietersen heard the news when it was announced on Saturday, which will leave Flintoff on the sidelines for the next three months, ruling him out of the remainder of the Test and one-day series against Pakistan. He is also a major doubt for October's Champions Trophy in India.
But Pietersen stressed: "This creates an opportunity for the youngsters and creates opportunities for someone else to come in, do well and play for England.
"It will be a pretty big series to win without Freddie but we will be giving everything we can to beat Pakistan."
Pietersen conceded that missing Flintoff will be "a big blow, but injuries are injuries and it's just a case of wishing him well."
He added: "We hope he will get himself right, to get back on that field for the Ashes, which he says he will do. He's a big influence on the dressing room. He messes around and jokes about and he will be someone that is missed."