Pietersen hit his 23rd Test hundred, and first in Manchester, to help England close day three on 294 for seven.
Despite that still representing a deficit of 233 runs, and 34 short of the follow-on, Pietersen believes England are now safely in position to at least get the draw they require over the next two days to retain cricket's oldest trophy.
In fact the bullish right-hander believes England can even look to go on and win the match after Australia's bowlers were forced to toil for their five wickets on a placid-looking pitch.
"(We are in a position of) safety if not winning the Test match," he said on Saturday. "We've seen today that the wicket is still pretty good.
"If our engine room, as we like to call it, apply themselves tomorrow and we get as close as we can to their score, there's no reason why we can't (win) because we've put a lot of work into their big fast bowlers today."
Despite Pietersen's optimistic assessment of England's position, Matt Prior and Stuart Broad will resume on Sunday with the primary target of avoiding the follow-on.
That mark would seemingly represent Australia's best chance of pushing for the victory they need to keep their Ashes hopes alive, especially with rain forecast for the final two days.
England's lower order were left with the important task when Pietersen fell in the final hour in slightly controversial circumstances after hitting 113.
The right-hander was given out lbw to Mitchell Starc (three for 75), a decision upheld by TV umpire Kumar Dharmasena despite Hotspot appearing to show the slightest of edges on Pietersen's bat.
Snickometer, which is not available to the officials, also indicated he made contact although Pietersen refused to be drawn into any notion of yet another decision review system controversy.
"Two things from that decision. I thought I heard two noises and also I thought it pitched outside leg," he said, although Hawk-Eye suggested the ball did pitch in line. "But it is what it is. I'm out; it doesn't matter. I'm not getting involved in DRS."
Until today Pietersen had been largely absent with the bat, after only returning from a knee injury on the eve of the series.
The 33-year-old claimed that the problem, which forced him home early from the tour of New Zealand in March, had almost forced him to undergo surgery which could have ruled him out of this and the return Ashes series in Australia later this year.
"If I'd had surgery I'd have been out for nine months," he said. "(It was) a big decision. I think I'll be in rehab for the rest of my career unfortunately. I'm just an old man, with sore calves and sore hamstrings. I'm fine."
England will be thankful that Pietersen opted not to go under the knife if Saturday's innings does prove vital in ensuring the Ashes are retained in Manchester. Should that be the case Pietersen admitted he would be able to savour two personal milestones that came with the innings.
The 33-year-old became England's leading runscorer in all formats, surpassing Graham Gooch's mark of 13,190, while he also moved clear in second place on the list of England's Test centurions - two behind skipper Alastair Cook.
"Wow. I didn't know, so it feels good," he said. "Personal achievements are fantastic and everyone wants to have personal achievements, nice achievements. I've just got to wait for that to sink in - it's quite interesting. It's something nice."
Australia quick Starc believes his side are still firmly in the hunt to press for victory, despite still needing to take 13 wickets.
So far the Old Trafford pitch has yielded just 14 wickets in three days, but Starc is confident that the bowlers will start to be rewarded by a slowly deteriorating surface on Sunday.
"I think things are going to happen pretty quickly on the last two days," he said. "It's showing signs of more and more turn and it's only going to turn more heading into the end of the Test.
"Things are going to happen quickly in the third and fourth innings but there's a few wickets to get yet, but we're up for the challenge."