Jean-Eric Vergne was furious with himself after missing out on a chance to shine in Q2 for the Korean Grand Prix. The Toro Rosso driver instead ended the session 17th fastest.
Vergne set the fastest first sector time of all in the final moments of the middle segment of qualifying, before ruining his lap with a mistake at the final corner.
"The performance looked very good and competitive this afternoon, but unfortunately I tried to take the final corner flat on my very last run, but I got it wrong and ruined my lap, nearly losing the car, so I am angry with myself for that," he said.
"The step up in performance compared to yesterday came partly from improving the car overnight and again since FP3 and partly from myself, in the way I was driving."
Vergne also had to give away time in middle sector during that lap, as ironically it coincided with teammate Daniel Ricciardo being forced to stop at the side of the track.
"I simply lost drive coming out of Turn 12, feeling as if the car was in neutral and I couldn't find any gears," said the Australian, who qualified 16th. "I could not bring the car back to the pits and had to abort the run at the side of the track. A shame, because Q1 went very well and I was able to post a competitive time.
"I don't know if I could have eventually got into Q3, but whatever the result, this has been a missed opportunity."