Red Bull chose to only make one run in the primary segment of Melbourne qualifying.
Moving into the final moments, it sat third with Max Verstappen and with Gasly.
But improvements from the majority of the rest of the field pushed down them the order.
Though Verstappen still made it right to Q 2 at 10th, Gasly – just 0.144 minutes non – was 17th and eradicated.
“We’ve been somewhat optimistic with one run and I am really, very disappointed with this,” Gasly told BBC Radio 5 Live.
“This was our strategy. I was pretty content with my very first lap, wound one up behind Max, therefore just lost a little bit.
“We simply didn’t expect others to improve so far on the run.”
Gasly said he knew as soon as he watched other drivers’ second-run days that moving out at Q1 was a powerful possibility.
“Once I watched that the improvements that they were doing, they certainly were winning almost a moment, I quickly realized that it’d be pretty tough,” Gasly added.
“It’s disappointing because FP3 had been better, I felt comfortable with the vehicle in qualifying and that I think we all had the pace to get a decent outcome.
“We got caught out by track development plus it cost us alot .”