The colt claimed Epsom's Coronation Cup a neck ahead of 7/4 favourite and runner-up Al Aasy after a terrific battle, and was later rested instead of a shot at the Hardwicke Stakes during Royal Ascot.
"After his run at Epsom I thought we'd had a hard race and I thought it (Royal Ascot) might come a bit quick, so I made a conscious decision that I didn't want to run him after a hard race," said trainer William Muir.
"Then come confirmation time he was nearly bursting the place open and I thought 'oh goodness, what do I do?' - but then I thought 'no, stick to your original plan'.
"He could have run because he was really, really fresh and well, he was jumping out of his skin.
"I think he could have taken the turnaround, but I want to space these races out because he could go anywhere and if I run him too many times in quick succession, will we get through to the Arc and those type of races at the back end of the year?
"I didn't want to punish him, he's a very good horse and I want to train him as a good horse, which I always would do with any animal.
"I don't want to just run him in and out because he's not here for that, he's a very good animal."
Pyledriver will bid for a second Group One success when he takes on the King George, run like the Coronation Cup over a mile and a half.
"At the moment he's like a lion, we're going to go for the King George," Muir said.
"He's in really good shape, he's fresh as paint."
Muir and Grassick's stable star has become one of racing's most popular success stories, something Muir attributes to the tale of his failure to sell as a foal and the underdog status he has gained from being trained by a smaller yard.
"He's very popular because he's very eye-catching and good looking," he said.
"He does what he does and people like the story with a smaller stable.
"He's a horse that wasn't worth anything and he's graduated to be a star performer."