With the series balanced at 1-1, England need to win to regain the Ashes in what is Flintoff's final Test match beginning on Thursday.
Much focus is on the 31-year-old, who expects to be fit to face the Aussies, but he claimed the series situation should override that.
He said: "The occasion - 1-1 in an Ashes series, having a chance to win the Ashes at The Oval - is huge.
"It's my last Test, but I'm not too fussed about that. It's more the chance to win the Ashes again.
"I'm not the first person to announce Test retirement during a series and I'm sure I won't be the last but the occasion is bigger than that."
Flintoff, who missed the drubbing at Headingley because of his long-standing knee injury, is confident he will be fit to play come Thursday.
"I've been working with [physio] Dave Roberts, had some batting over the weekend, and today a bowl. I'm confident I'll come through.
"I'm probably in a better state than I was going into the last Test [at Edgbaston]. I think I'm more or less there, I just have to prove it."
Flintoff does not think the innings-and-80-run defeat in Leeds will play too much on the players' minds.
He said: "I think the week off has been important for the lads. You talk about momentum - it seems to be the buzzword of the minute - but this is a one-off test match."
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