The Aussie trainer always held Guineas ambitions for Mighty Boss right from when successful in a Sale maiden in July.
For Walker the group one win was the result of hard work after being sidelined through injury for a large part of the year.
He needed a back operation and has only been back riding during the past two months. "Over the last two or three years I've had six months on, two months off with operation after operation," Walker said. "My weight got out of control when that's happened but my body's strong at the moment. I'm light and I'm hungry."
Walker has been riding work at Caulfield every Tuesday since his comeback.
After winning on Main Stage at Flemington last week, he walked past Price asking if there was a chance of getting a ride on a good horse in his stable. "He said, 'I don't have any', but I said don't worry, I'll keep turning up every Tuesday," Walker said.
"This is a huge thrill. Whenever I've had lean times he's always been a great supporter."