Castroneves clocked a sizzling four-lap average qualifying speed of 227.970 mph to capture his fourth pole for the May 30 race, tying him for second with A.J. Foyt and Rex Mays on the all-time list. Rick Mears holds the record for most Indy 500 poles with six.
"This place, you've got to expect the unexpected, that was a great result," Castroneves, who is trying to become the fourth driver to win four Indy 500s, told reporters. "It's very tough to compete at this level to go sometimes over the limit.
"Sometimes today it was not fun but you've got to do what you've got to do. I saw Jesus three times out there. From 225 to 227 it's a big difference."
A new qualifying format saw the top 24 drivers Saturday locked into the 33-car field with the remaining nine spots to be filled Sunday.
Adding more drama to the day, the nine fastest cars returned to the track late in the afternoon for what was billed as the Fast Nine shootout to determine the pole sitter.
Castroneves was first out onto the speedway and set a pace no one came close to matching.
Three female drivers qualified for spots on the grid and two more could be added to the field Sunday. Brazil's Ana Beatriz produced the best qualifying effort among the women putting her car on the outside of row seven with the 21st best time.
It has been a bitterly disappointing season for Patrick, who heard unfamiliar boos at the Brickyard when she stepped out of the cockpit following her qualifying effort. She blamed the poor performance on her car during a trackside interview broadcast on the public address network.
"This is the worst car I've ever had," scowled Patrick.
"The cars aren't good, they're really bad. "I'm not an engineer, there's no stability, no grip. It's scary, it's really scary. I just wish it was over now, it's awful."
Venezuelan Milka Duno and American Sarah Fisher failed to crack the top 24 but will try again Sunday to grab one of the last nine spots to put a record five women in the field.
"This is the first year I have really been racing against women," said de Silvestro. "I'm not really paying attention about what they do or if I am the one to qualify better.
"My goal is to beat all the 33 drivers."
(Writing by Steve Keating in Toronto; Editing by Peter Rutherford)