The German was on course for the victory in Azerbaijan, comfortably ahead of the Mercedes drivers.
That, though, all changed when a late Safety Car handed Valtteri Bottas a free pit stop and the lead.
Vettel tried to attack him on the restart only to lock up and run wide.
He fell to third and then fourth as his flat-spotted tyres meant he could not defend against Sergio Perz.
"I'm happy I tried but not happy it didn't work," he said of his attempted pass for the lead.
"I don't think it was overly optimistic to jump on the inside but I was a bit trapped as I couldn't see where I was in relation to Turn 1.
"Obviously I see Turn 1, we have a reference on the right but on the left there is hardly every reference.
"Once I jumped on the inside I locked up but I wasn't overly late.
"I made it, just.
"Other than that I think it was a strong race and that's how it goes some times."
