Power topped the 45-minute session around the 13-turn, 2.258-mile road course with a best lap of 1m06.4905s.
Andretti Autosport’s Colton Herta set the early pace at 1m07.7772s before a red flag for Pagenaud’s huge somersault at Turn 4, the Frenchman immediately radioing-in to report that he’d suffered a complete brake failure.
His Meyer Shank Racing car was launched over the grass verge at the end of the 180mph straight and landed in the gravel trap, which is nicknamed ‘China Beach’ and situated on a downslope due to the topography of the track.
Pagenaud barrel-rolled violently six and a half times before bouncing off the tyre wall, and all four corners of his car were damaged. The AMR safety crew rushed to his aid across the giant gravel trap, his car having come to rest on its side but at an angle he couldn’t climb out from unassisted.
After releasing him from the car, he took a moment to sit on the gravel before getting to his feet. He took another moment to crouch down before being led to the medical car by the series’ doctor.
Although the cause was very different, the outcome was very similar to Michael Andretti’s incredible crash here in the 1998 race from which he also walked away.
The session restarted with 26 cars on the tight and twisty track, making it almost impossible to get a clear lap early on.
Romain Grosjean (Andretti Autosport) had a near miss when he caught the train of cars that were coasting to get a gap, just swerving around Juncos Hollinger Racing’s Agustin Canapino.
Once the field began to pit, some proper running became available, with Rahal Letterman Lanigan Racing’s Graham Rahal leading the way with 1m06.884s from David Malukas, who’s stated he won’t be back with Dale Coyne Racing next year – fuelling speculation that he’s heading to Chip Ganassi Racing next season.
Friday pacesetter Pato O’Ward (Arrow McLaren) then took over the top spot with 1m06.7947s, ahead of Ganassi’s Scott Dixon – who’d recovered from an earlier spin at Turn 5.
Herta returned to P1 with 1m06.7791s before Power beat that with 1m06.4905s, a quarter of a second ahead of Alex Palou (Ganassi).
Herta stayed third, ahead of O’Ward, Dixon, Scott McLaughlin (Penske), Rahal and Malukas.
Santino Ferrucci caused a second red flag when he nosed his AJ Foyt Racing entry into the tyre wall at Turn 12.
Qualifying starts at 2:45pm local time.