"Even the scoreboard went against him the other night, which I find very strange.
"But it's good to see he's come through it and scored very well. It hasn't affected him - in fact, it's probably played right into his hands because it's the kind of thing that motivates him.
"He likes that kind of challenge, and that's good for the future."
Pietersen is the sort of cricketer who can expect to be targeted by opponents and rival supporters whoever he is playing against. And, as Fletcher says, he seems to thrive on being baited.
Why else would he choose to have a broad orange streak put in his hair midway though this series? Not because he wanted to merge into the background, that is for sure.
But it's all very well being bullish when your game is going well. Pietersen's next test will come when he runs into a trough of poor form. Again, the signs are encouraging.
"I was interested in watching him in Zimbabwe earlier this winter when he got a first-ball duck," said Fletcher. "Then, within 10 minutes of being in the field, he dropped a catch.
"I just wanted to see his body language, and it never altered. He was still positive, urging everyone on and clapping and shouting. That to me is what it's all about."
Pietersen has pledged his future to England, rather than to South Africa. The same can be said of Fletcher, too, following his dismissal of "paper talk."
South Africa are inviting applications for the job of coach, but Fletcher says he will not be applying despite rumours that the position might interest him.
South Africa v England, Buffalo Park, today, 12.30pm (live on Sky Sports 2)
