Lewis Hamilton's Ferrari misery drags on after the Brit qualified only 12th for the Azerbaijan GP - despite thinking he could get pole position.
The 40-year-old said he was 'so disappointed' and pointed to a strategy shortcoming for their latest letdown.
Hamilton was knocked out in Q2 on the soft tyres - an unfamiliar C6 compound - while his rivals including team-mate Charles Leclerc set faster times on the medium C5s.
The C5s have a negligible performance gap to the C6s and lasted better in qualifying, leaving Hamilton to struggle on the unpredictable compound.
It is a major disappointment after he and Leclerc bossed the second practice session, coming first and second in that, and leaves him with a mountain to climb amid a tricky debut season for the Scuderia in which he placed sixth in the drivers' standings.
'Honestly, I'm obviously so disappointed,' Hamilton said.
Lewis Hamilton says he is 'so disappointed' after qualifying 12th for the Azerbaijan GP
'Yesterday the car was feeling good, today there was some direction that we ended up going which on paper looked like it was the best place for us to be.
'And ultimately, our pace had been good, we'd been progressing, I was feeling really on it, didn't make any mistakes, you didn't see me go down any exit roads, it was just that we didn't have the right tyre on at the end – and it's tough.
'Everyone ahead of me basically had the medium tyre on, but I lost a medium tyre in FP2 and due to our run plan, and that put me on the back foot.'
Could he have taken one of the C5s being held back?
'I wanted to,' he said. 'But they said that the warm-up was too long or something like that, so then we ran out of time and then ran out of fuel.
'So not great, but we'll take it internal. As I said, there's been lots of positives from this weekend, I've really felt on it. I honestly thought I was going to be shooting for a pole today and so it's kind of a bit of a shock, but I'll take it on a chin and keep trying.'
His team-mate, Charles Leclerc, did not fare much better in 10th.
Hamilton has had a mixed return to the grid since the summer break, having to retire from the Dutch Grand Prix before finishing sixth at Monza.